Inovasi-Vol19-3-Des2011 by Inovasi Online

Vol. 19 No. 3 (Desember 2011)

Majalah Ilmiah Persatuan Pelajar Indonesia Jepang

io.ppijepang.org

KECERDASAN SOLUSI HIDU

â&#x20AC;&#x2DC;Risetdan

Pengembangan

Material Lanjut â&#x20AC;&#x2DC; Topik Utama

Measurement of Elastic Bending Modulus of Metallic Foam under Static and Dynamic Loads with Improved Accuracy

Teknologi

Optimasi Pembuatan Pulp Serabut Sawit (Elais guineensis) melalui Proses Hidrolisis dengan NaOH

Khusus

Artikel pemenang TICA 2011 Cluster-1: Business, Social Science & Urban Planning

PPI JEPANG ISSN 2085-871X

DEWAN EDITOR MAJALAH INOVASI PPI JEPANG Pembina: Prof. Dr. Edison Munaf Atase Pendidikan Kedutaan Besar Republik Indonesia, Tokyo, Jepang Penanggung Jawab : Presidium Persatuan Pelajar Indonesia Jepang Andi Subhan Mustari (Toyohashi University of Technology) Atus Syahbudin (Ehime University) Fatwa Ramdani (Tohoku University) Editor Utama : Arief Yudhanto (Tokyo Metropolitan University) Staf Editor : Cahyo Budiman (Osaka University, Institut Pertanian Bogor) Nirmala Hailinawati (Tokyo Institute of Technology) Maharani Hapsari (Nagoya University, Universitas Gadjah Mada) Joni Jupesta (United Nations University, Tokyo) Oce Madril (Universitas Gadjah Mada) Muhammad Ridlo Erdata Nasution (Tokyo Metropolitan University) Retno Ninggalih (Sendai, Tohoku) Pandji Prawisudha (Tokyo Institute of Technology) Desain Grafis : Banung Grahita (Tokyo Metropolitan University, FSRD ITB) Foto Cover: Farid Triawan (Tokyo Institute of Technology) Website Admin: Bayu Indrawan (Tokyo Institute of Technology) Pandji Prawisudha (Tokyo Institute of Technology) Reviewer Tamu: Dr. Muhammad Ridha (National University of Singapore) Website: io.ppijepang.org E-mail: editor.inovasi@yahoo.com Alamat: Atase Pendidikan, Kedutaan Besar Republik Indonesia â&#x20AC;&#x201C; Tokyo, 5-2-9 Higashi Gotanda, Shinagawa-ku, Tokyo 141-0022, Jepang Tel: +81-3-3441-4201 Ext. 240, 241, 242, 243 Fax: +81-3-3280-5609 Website: www.atdikbudtokyo.com

Tentang INOVASI INOVASI, atau lebih dikenal dengan nama Inovasi Online (IO), adalah berkala dwibahasa yang diterbitkan oleh Persatuan Pelajar Indonesia di Jepang (PPIJ) sejak bulan Agustus 2004. INOVASI merupakan berkala ilmiah semi-populer yang berfungsi sebagai media untuk mengartikulasikan ide dan hasil riset dalam rangka memperkaya wawasan dan khazanah ilmu pengetahuan. INOVASI menyajikan artikel-artikel yang ditulis dalam Bahasa Indonesia atau Bahasa Inggris. Artikel tersebut mengisi topik utama (yang selalu berganti setiap nomor), dan topik lainnya, misalnya Ilmu Pengetahuan dan Teknologi, Sosial, Ekonomi, Politik, Bahasa, Psikologi, Pertanian, Bioteknologi, Kelautan. INOVASI diterbitkan tiga kali dalam setahun, yaitu bulan April, Agustus, dan Desember (ada tiga nomor dalam satu volume), dan didistribusikan secara online lewat mailing list PPIJ dan website INOVASI (http://io.ppijepang.org). Hingga sekarang, INOVASI telah menerbitkan sebanyak 20 edisi. INOVASI telah mempunyai International Standard Serial Number (ISSN) melalui Dirjen Pendidikan Tinggi sejak Agustus 2004.

ISI Tentang INOVASI

Isi

Editori@l Arief Yudhanto (Editor)

Topik Utama Measurement of Elastic Bending Modulus of Metallic Foam under Static and Dynamic Loads with Improved Accuracy Farid Triawan, Kikuo Kishimoto, Tadaharu Adachi, Kazuaki Inaba, and Toru Hashimura

Thickness Effect on the Damage Mechanism in Stitched Carbon/Epoxy Composites containing Circular Holes Arief Yudhanto, Naoyuki Watanabe, Yutaka Iwahori

Monitoring Secondary Bending Failure of Bonded Composite Panels under Tension Load using Fiber Bragg Grating (FBG) Sensors Agus Trilaksono, Naoyuki Watanabe, Hikaru Hoshi, Shin-ichi Takeda, Yutaka Iwahori

Teknologi Optimasi Pembuatan Pulp Serabut Sawit (Elais guineensis) melalui Proses Hidrolisis dengan NaOH Andrian Wahyu Jati, Nela Agustin K, Exsien Setyorini

Khusus: Artikel Pemenang TICA 2011 (Cluster I) First Prize | Analysis of Damping Effectiveness as a Link Between Shear Wall â&#x20AC;&#x201C; Shear Frame in Dual System Structure Yoas Yuniananta, Jessica Gunawan

Second Prize | Impact of Destination Images and Evaluative Factors Toward Touristsâ&#x20AC;&#x2122; Behavioral Intention of the Destination. Case Study: Old Batavia (Kota Tua) Taman Fatahillah Jakarta Anna M.Pratiwi and Hapsari Setyowardhani

Third Prize | Hidden Pattern Average : A New Technical Indicator for Securities Price Pattern Prediction Fietra Riva Harvadi

Finalis 1 | Performance Evaluation of Shear Wall System in Reinforced Concrete Tall Building Viktor Hugo Juanda

Finalis 2 | The Role of Vocational High School in Improving National Competitiveness: Analysis and Recommendation Budiono, Harizah Persiana Mangkunegara, Ayu Yeriesca

Panduan Penulisan Naskah untuk Majalah Inovasi Online

vol.19 no.3

EDITORIAL Arief Yudhanto, Editor

E-mail editor-inovasi@yahoo.com

disi Inovasi Volume 19 Nomor 3 menutup tahun 2011 dengan memuat topik utama, yaitu material lanjut (advanced materials). Secara sederhana, material lanjut didefinisikan sebagai bahan yang sifat-sifatnya lebih baik daripada

bahan biasa. Sifat-sifat yang dimaksud adalah ketangguhan (toughness), kekerasan (hardness), ketahanan lelah (fatigue strength), ketahanan tumbuk (impact strength), keuletan (ductility), tahan korosi dan lainnya. Ketika suatu produk dibuat dengan material lanjut maka produk akan mempunyai kualitas yang lebih baik jika sifat-sifat di atas dapat dimanfaatkan sesuai fungsinya. Misalnya, penggunaan paduan aluminum atau bahan komposit untuk sayap pesawat terbang; penggunaan pelat berlapis (sandwich) untuk bahan membuat loudspeaker atau papan selancar; penggunaan serat Kevlar速 dan keramik untuk baju anti peluru; penggunaan paduan ingat-bentuk (shape-memory alloy) untuk meredam kebisingan mesin; penggunaan carbon nano-tube untuk otot buatan atau transistor.

Figure 1 (a) Bahan komposit untuk sayap Boeing 787 yang dibuat oleh Mitsubishi Heavy Industries (mhi.co.jp), (b) loudspeaker 1007Be sandwich buatan Focal (focal.com), (c) adaptive chevron di bagian pengeluaran mesin pesawat yang dibuat dengan shape memory alloy (nasa.gov).

Sejumlah perusahaan melakukan riset mandiri atau bekerja sama dengan institusi/ universitas untuk mengembangkan material lanjut. Ada setidaknya 10 material lanjut yang menjadi tumpuan teknologi masa depan: aerogel, carbon nano-tube, metamaterial, intan ukuran besar (bulk-diamond), fullerene ukuran besar (bulk fullerenes), logam amorf (amorphous metal), paduan super (superalloys), buih logam (metal foam), alumina tembus pandang, dan e-textile1. Material-material tersebut akan dapat diterapkan dalam bidang energi (sistem penyimpanan), transportasi (pesawat, mobil, kereta), konstruksi raksasa, bahan daur ulang, bahan biomedik dan teknologi komputer2.

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Salah satu material lanjut yang mendapat perhatian peneliti Jepang adalah metal foam. Metal foam yang terbuat dari paduan aluminum diteliti di Kishimoto Laboratory, Tokyo Institute of Technology. Seorang mahasiswa doktoral, Farid Triawan, menghadapi kenyataan bahwa standard pengukuran untuk metal foam dengan akurasi yang baik tidak tersedia. Triawan bersama koleganya mengembangkan metodologi yang sederhana untuk mengukur sifat mekanik metal foam ketika mendapat beban statik dan dinamik3. Tokyo Metropolitan University dan Japan Aerospace Exploration Agency bekerja sama untuk meneliti bahan komposit karbon/epoksi dengan penguatan tiga dimensi. Penguatan 3D ini dilakukan dengan cara menjahit bahan komposit dengan serat yang kuat (Vectran速) dan bahannya dinamakan stitched composite. Dengan jahitan, kekuatan luar bidang (out-of-plane strength) komposit menjadi lebih baik, namun kekuatan dalam bidang (in-plane strength) boleh jadi menurun. Yudhanto dkk. membahas tentang pengaruh dua faktor penting dalam desain struktur pesawat terbang (ketebalan dan adanya lubang lingkaran) terhadap perambatan kerusakan pada komposit jahit tiga-dimensi4. Tantangan penggunaan komposit karbon atau gelas di pesawat terbang adalah masalah pemantauan kerusakan (damage monitoring). Kerusakan pada komposit sangat rumit karena melibatkan banyak modus sedangkan kerusakan ini biasanya tersembunyi. Oleh karena itu, diperlukan sebuah metode yang dapat memantau kerusakan dalam komposit secara detil dan waktu-nyata (real-time). Trilaksono dkk. membahas tentang pemantauan kerusakan pada sambungan komposit dengan menggunakan sensor optik Fiber Bragg Grating (FBG). Sensor ini ditanam diantara sambungan dan dapat memberikan indikasi kerusakan secara waktu-nyata5. Di atas semua itu, tantangan penggunaan material lanjut adalah masalah ramah lingkungan. Material lanjut diharapkan tidak menimbulkan polutan yang di luar batas. Selain itu, material lanjut harus dapat dibuat dengan bahan yang berkelanjutan (sustainable) atau dapat dihasilkan terus-menerus tanpa mengganggu keseimbangan sumber daya alam. Dua tantangan itu, ramah lingkungan dan berkelanjutan, perlu dijawab dengan kerjasama multidispliner antara ilmuwan, teknolog dan desainer.

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Tokyo Tech Indonesian Commitment Award 2011 Inovasi kali ini juga mengetengahkan artikel ilmiah yang menjadi pemenang dan finalis Tokyo Tech Indonesian Commitment Award (TICA) 2011. TICA didirikan pada 2010 oleh PPI Tokodai (Tokyo Institute of Technology) untuk meningkatkan minat terhadap pengembangan sains dan teknologi. TICA mengundang para mahasiswa/i di Indonesia untuk menuliskan hasil riset mereka dalam sebuah artikel. TICA 2011 terbagi dalam tiga cluster, yaitu (1) Business, Social Science and Urban Planning, (2) Electronic-Electrical and Information Technology, (3) Applied Science and Technology. Dalam nomor ini, kami menampilkan lima artikel dari Cluster 1: tiga artikel pemenang dan dua artikel finalis. Selamat membaca dan semoga bermanfaat

Referensi 1. Anissimov M. Accelerating Future: 10 Interesting Futuristic Materials. Lelaman: http://www.acceleratingfuture.com/michael/blog/2008/04/ten-futuristicmaterials/ (diakses pada 30 Desember 2011). 2. Apelian D. Looking beyond the last 50 years: The future of materials science and engineering. Journal JOM, The Minerals, Metals and Materials Society, February 2007. 3. Triawan F, Kishimoto K, Adachi T, Inaba K, Hashimura T. Measurement of elastic bending modulus of metallic foam under static and dynamic loads with improved accuracy. Inovasi, Vol 19 No 3, hal. 4. Desember 2011. 4. Yudhanto A, Watanabe N, Iwahori Y. Thickness effect on the damage mechanism in stitched carbon/epoxy composites containing circular holes. Inovasi, Vol 19 No 3, hal.16. Desember 2011. 5. Trilaksono A, Watanabe N, Hoshi H, Takeda S, Iwahori Y. Monitoring secondary bending failure of bonded composite panels under tension load using Fiber Bragg Grating (FBG) sensors. Inovasi, Vol 19 No 3, hal.33 . Desember 2011.

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TOPIK UTAMA Measurement of Elastic Bending Modulus of Metallic Foam under Static and Dynamic Loads with Improved Accuracy Farid Triawan1*, Kikuo Kishimoto1*, Tadaharu Adachi2, Kazuaki Inaba1, and Toru Hashimura3 1

Department of Mechanical Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552, Japan

Department of Mechanical Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi-shi, Aichi 441-8580, Japan

Materials, Process and Applied Mechanics Res. Sec., Technical Department, Aluminum & Copper Company, Kobe Steel, LTD., 5-5 Takatsukadai 1-chome, Nishi-ku, Kobe, Hyogo 6512271, Japan

*Email: triawan.f.aa@m.titech.ac.jp (F. Triawan); kkishimo@mep.titech.ac.jp (K. Kishimoto)

ABSTRACT: Metallic Foams suffer from lacking of standardized measurement technique for characterizing its mechanical properties and behavior. This article introduces improved methodology of static bending tests, i.e. three- and four-point bending tests, to measure the elastic bending modulus with high accuracy. The measurement error caused by the local deformation undergone by the specimen at the indented and supported locations is effectively reduced by determining the elastic modulus from the unloading processes. The elastic moduli measured from the static bending tests are compared with those measured from the dynamic bending test. The results exhibit high correlation with standard deviation of less than 5.4%; indicating the introduced methods is highly reliable and accurate. KEYWORDS: measurement, metallic foams, elastic modulus, bending, accuracy

1. INTRODUCTION Metallic Foams suffer from lacking of standardized measurement technique to precisely identify its mechanical properties and behavior. Various methodologies and techniques had been studied and proposed [Ashby et al. (2000), Banhart (2001)]; however, measurement technique for characterizing the elastic behavior

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under bending has not yet been well defined. The measurement techniques introduced by, for instance, Lakes (1983, 1986) and Yen et al., (2010) are considered to be too complicated though accurate enough. Lakes (1983, 1986) conducted the measurement using electromagnetic force which requires complex measurement apparatus, while Yen et al. (2010) introduced the moiré method which needs complicated data analysis to improve the measurement accuracy of three-point bending test. The work presented in this paper introduces much simpler methods for measuring the elastic bending modulus with high accuracy using static and dynamic bending tests. In the static test, the conventional three- and four-point bending tests are conducted with a number of modifications in its methodology and measurement system; while in the dynamic test, the flexural vibration test is carried out for verification and comparison study.

2. FOAM MATERIALS Closed-cell aluminum alloy foams (Alporas, Shinko Wire) with different densities and cell characteristics were used as the basic material for making the specimens. The specimens were cut from blocks of Alporas with size of 300 × 210 × 50 mm3 using wire-cut electrical discharge machine to ensure flatness and clearness of the cutend; and then weighed to identify its density. According to the density value, the specimens were grouped into four, Foam A, B, C, and D, which its cell-characteristics are tabulated in Table 1, and its cross-sectional pictures are shown in Fig. 1. We defined cell-face as the wall of the cell, whilst cell-edge as the meeting point where two or more cell-faces assemble each other; thus cell-edge is always thicker than the cell-face as denoted by Fig. 2. In addition, the cell-diameter of each foam material was measured based on ASTM E112. Table 1: Foam materials

Foam Density, kg/m3

Cell diameter, mm Cell-face thickness, mm

A 177 ± 7 B 222 ± 4 C 258 ± 10 D 346 ± 7

3.98 ± 0.09 4.30 ± 0.11 2.82 ± 0.10 2.90 ± 0.07

0.05 – 0.10 0.01 – 0.20 0.01 – 0.20 0.05 – 0.70

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Table 2 shows the beam-specimen dimensions used in the experiments. Considering the cell-diameter of many metal-foams used in engineering applications is between 1 and 10 mm, where it is common to have components with dimensions of only a few cell-sizes, the specimens used in the present work were thus prepared to have a thickness (height or width) of between 10 and 30 mm. The length to thickness ratio was set to be bigger than 10:1 as required by Bernoulli-Euler beam theory to generate nearly pure bending deflection during the tests. Three to five specimens of each foam material were prepared for every test.

Fig. 1: Closed aluminum alloy foams; (a) Foam A; (b) Foam B; (c) Foam C; (d) Foam D.

Fig. 2: Description of cell-edge and cell-face of the cell

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Table 2: Foam specimens

Test Foam Length, mm

Dimensions Height, mm

Width, mm

Static Tests

300

(3- and

300

4-point

300

Bending)

300

Dynamic Test A

200, 300

20, 30

(Flexural

100, 150, 200, 250, 300 10, 20

10, 20

Vibration)

200, 300

20, 30

20 30

3. EXPERIMENTAL PROCEDURES 3.1. Static Bending Test In the static bending test, the elastic bending modulus, Ef, was measured using the conventional method of three- and four-point bending tests. At first, we applied the standardized measurement techniques given by ASTM E290, ASTM D790, and ISO 178. However, these techniques were found not suitable for foam material because it did not consider the measurement error caused by the local deformation occurred on the specimen surface due to the applied loads from the load applicator and the supporting jigs. Figure 3 shows the example picture of local-deformation occurred on polymeric foam due to the applied load. Open-cell structure of the specimen surface has lower stiffness than that of the closed-cell bulk in the body. The low stiffness of the specimen surface leads to the local-deformation at the position where the load were indented or the supporting jigs were placed. This local-deformation then produced error in the total measured deflection as also reported by Yen et al. (2010). Thus, instead of using the standardized measurement techniques, we conducted the tests by our self-developed measurement apparatus which was designed to minimize the error caused by the local-deformation.

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Fig. 3: Local-deformation occurred on the specimen surface due to load which generates error on the measured beam deflection [Yen et al. (2010)].

Figure 4 shows the measurement apparatus of the three- and four-point bending tests. The supports were made of cylinder-shaped stainless steel with 20 mm diameter and were fixed to the ground by screws and bolts. The supports were deliberately shaped as cylinder in order to increase the contact area with the specimen; and the diameter was set to be 20 mm since the bigger the diameter the bigger the contact area. By doing this, the local deformation caused by the supports can be minimized. The specimens were loaded using 1 mm diameter nylon ropes that are connected to weights (see Fig. 4). The maximum deflection caused by the weights was measured by laser displacement sensor (Keyence LK-G400). A white and small piece of paper attached by adhesive tape on the specimen surface was used to reflect the laser. The weights were not allowed to move or swing during testing to ensure measurement stability. Furthermore, in order to fix the loading position, we put a 0.5 kg weight as a preload. Laser Displacement Sensor L/2 Laser

L/2

Beam Specimen

Nylon-rope Weights L = 276 mm

(a)

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Laser Displacement Sensor L/2 Beam Specimen

Laser

L/4

Nylon-rope

L/4

Weights L = 276 mm

(b)

Fig. 4: Experimental set-up of (a) 3- and (b) 4-point bending tests

Unloading processes were performed 3–5 times during the test of every specimen for evaluating the unloading effect on the elastic bending modulus. Eqns. (1) and (2) of three- and four-bending tests, respectively, were used for calculating the elastic modulus value. The maximum stress and maximum strain of the specimen at L/2, e.g. for three-point bending test, were calculated by Eqns. (3) and (4), respectively, which is based on Bernoulli-Euler beam theory (Timoshenko et al., 1985).

Ef =

PL3 48dmaxI 11PL3

(1)

(2)

348dmaxI

smax = +

emax = +

PLh 8I 6dmaxI L2

(3)

(4)

where, P is the load applied to the specimen (see Fig. 4), L is the support span, I is the second moment of area, h is the thickness of the beam, δmax is the maximum beam deflection, and “±” represents the compression and tension condition.

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3.2.

Dynamic Bending Test

Flexural vibration analysis was performed for verifying the measurement results of the static bending tests. This method was chosen because it can completely omit the error generated by the local deformation effect found in the static bending test. Ef was determined by measuring the natural frequency of vibration of free-hanging specimens in response to an impulse force. The tests were performed by exciting free-hanging specimens by an impact hammer (086B03, Piezotronics) with a steeltipped head as shown in Fig. 5. Vibration of the specimens were measured using an accelerometer (352C23, Piezotronics) attached to the specimen surface using adhesive glue (Alonalfa, Toagosei cyanoacrylate). Signals from the impact hammer and accelerometer were acquired by digital oscilloscope (DL716, Yokogawa) through a signal conditioner (480C02, Piezotronics). Fast Fourier transform method was applied to the measured vibration data to extract the first, second, and third flexural natural frequencies. The measured natural frequencies were confirmed to be independent of positions of the impact and accelerometer detection in preliminary experiment.

Front view

Yarn Beam Specimen

Impact Hammer

Signal Conditioner Front view

Side view

Oscilloscope

Accelerometer

Fig. 5: Experimental set-up of flexural vibration test

Ef of each specimen was calculated from the measured natural frequencies based on Bernoulli-Euler beam theory using Eqn. (5),

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 l2  r A E f =  2pf n 2   l n  I 

 l 2l2  r ArA  Ef == 2pfnn 2 E  l ln 2  I I  n

(5)

where fn is the flexural natural frequency, l is the specimen length, I is the second

moment of area, ρ is the density, A is the cross sectional area, and λn is the Eigen value constant related to the boundary conditions. Given free-free beam conditions,

values of λn for the first, second, and third flexural vibration modes are 4.730, 7.853, and 10.996, respectively.

4. RESULTS AND DISCUSSION 4.1. Static Bending Test Preliminary tests using stainless steel beam specimen, SUS 304, were done for validation of the developed measurement apparatus. The result showed good precision as the measured elastic modulus agreed well with elastic modulus value of SUS 304 with error of less than 10%. The typical stress-strain curves measured from three-point bending tests at L/2 using Foam A, C, and D is shown in Fig. 6. The curves describe the stress-strain condition at the bottom surface of the beam, which were calculated using Eqns. (3) and (4). The initial loading curve was found to exhibit relatively lower slope compared to those of the subsequent unloading or reloading curves. Furthermore, the unloading or reloading curves of every foam material were also found to demonstrate approximately constant slope relative to each other. The lower slope of the initial loading curve was most likely due to the local deformation of the specimen surface at the supported locations. Moreover, it might be caused by the effect from the plastic yielding of weak cell-face. Ashby et al. (2000), Sugimura et al (1997), and Ramamurty and Paul (2004) reported that the effect from plastic yielding of weak cell-face on the initial loading curve measured using uniaxial compression test could underestimate the elastic modulus value of metal foams. However, the effects from the local-deformation as well as the plastic yielding of weak cell-face seemed to vanish in unloading or reloading curves as indicated by the higher and constant slope. Therefore, we determined Ef from the deflection data measured in unloading processes using Eqns. (1) and (2).

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Fig. 6: Maximum stress-strain curves at L/2 of three-point bending test (Triawan et al. 2010)

4.2.

Dynamic Bending Test

Figure 7 shows the typical vibration data measured from a specimen of Foam B. The flexural natural frequencies, fn , were selected by evaluating the peaks of the curve. Figure 8 shows relationship between the selected fn and specimenâ&#x20AC;&#x2122;s length described by the Bernoulli-Euler beam theory for the first to third vibration modes. The data shows clear relation of as indicated by Eqn. (5), justifying its use as a basis for determining the corresponding values of Ef as illustrated in Fig. 9 for Foam B, where Ef â&#x20AC;&#x2122;s were found to be independent of the specimen length.

Fig. 7: Measured flexural natural frequency by dynamic bending test

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Fig. 8: Typical plot of measured natural frequencies to the specimen lengths (Triawan et al. 2010)

4.3.

Results Comparison of Static and Dynamic Tests

All measurement results are summarized in Table 3. As seen in the table, the measured Ef â&#x20AC;&#x2122;s demonstrate small value of standard deviation of less than 13% for

every test and every foam material. For the static bending test, this means that the improvements introduced in the test effectively reduced the error generated by the local-deformation effect; meanwhile, for the dynamic test, this means that the elastic moduli are confirmed to be independent of the measured flexural vibration

modes. Furthermore, Ef â&#x20AC;&#x2122;s measured by the static tests are also found to exhibit good correlation with those measured by the dynamic test, as denoted by small standard deviation of less than 5.4%. This indicates that we successfully improved the measurement accuracy of the conventional three- and four-point bending tests in measuring the elastic bending modulus.

Fig. 9: Measured Ef of Foam B plotted to the specimen lengths (Triawan et al. 2010)

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Table 3: Elastic bending moduli measured from all tests

Foam

Elastic Bending Modulus, E (MPa) f

3-Point Bending

Standard Deviation,%

Flexural Vibration

4-Point Bending

607 ± 76

666 ± 82

670 ± 65

5.4

–

966 ± 30

909 ± 74

4.3

1121 ± 80

1060 ± 96

1058 ± 109

3.3

1641 ± 201

1695 ± 34

1655 ± 154

1.7

“–“denotes no test

The current proposed method, however, might not give satisfactory results if it is applied to measure the plastic bending behavior. We might not get precise measurement results as the effect from local deformation would be much bigger when the specimen is loaded until plastic deformation. Further research on the improvement of the static bending test to accurately measure the plastic bending behavior of metal foam is required.

SUMMARY AND CLOSING REMARKS

In the present work, we measured the elastic bending modulus of metallic foams by means of static and dynamic bending tests. In the static tests, several improvements were introduced on the three- and four-point bending tests, while in the dynamic test, flexural vibration analysis were performed to measure the elastic bending modulus. Closed-cell aluminum alloy foam was used as the foam material. The low accuracy problem of the three- or four-point tests was effectively reduced. These are the improvements introduced in the tests: a. A relatively much larger diameter of the supporting bar/jig compared to the celldiameter was used; this can avoid the force to be concentrated at one point, so that it can minimize the local deformation occurred at the supporting points. b. Bending deflection of the beam specimen was measured by laser displacement sensor; this can avoid the measurement error caused by the local deformation due to the load applicator. c. Unloading-reloading processes were employed where the elastic bending modulus was determined from the unloading curves. These methods are obviously much simpler compared to those introduced by Lakes, (1983, 1986) or Yen et al. (2010) which require complex measurement apparatus or complicated data analysis. Verification on the measurement results was done by

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comparing Ef from the static and dynamic tests. The result demonstrates satisfaction with standard deviation of less than 5.4%; indicating the proposed improvement technique is highly reliable and accurate.

REFERENCES 1. Ashby M.F., Evans A., Fleck N.A., Gibson L.J., Hutchinson J.W., Wadley H.N.G., “Metal foams: a design guide”, Boston: Butterworth-Heinemann; 2000. 2. Banhart J., “Manufacture, characterisation and application of cellular metals and metal foams”, Progress in Materials Science, Vol. 46, pp. 559-632, 2001. 3. Lakes R.S., “Size effects and micromechanics of a porous solid”, International Journal of Solids and Structures, Vol. 22, pp. 55-63, 1986. 4. Lakes R.S., “Experimental micro-elasticity of two porous solids”, Journal of Material Sciences, Vol. 18, pp. 2572-2580, 1983. 5. Ramamurty U., Paul A., “Variability in mechanical properties of a metal foam”, Acta Materialia, Vol. 52, pp. 869-876, 2004. 6. Sugimura Y., Meyer J., He M.Y., Bart-smith H., Grenstedt J., Evans A.G., “On the Mechanical Performance of Closed-cell Al Alloy Foams”, Acta Materialia, Vol. 45, pp. 5245-5259, 1997. 7. Timoshenko S.P., Yang D.H., Weaver U., “Engineering vibrations” Moscow: Mashinostroenie; 1985. 8. Triawan F., Adachi T., Kishimoto K., Hashimura T., “Study on elastic moduli of aluminum alloy foam under uniaxial loading and flexural vibration”, Journal of Solid Mechanics and Material Engineering, Vol. 4, pp. 1369-1380, 2010. 9. Triawan F., Kishimoto K., Inaba K., Adachi T., Lin Z., Hashimura T., “Measuring the flexural modulus of metal foam”, Proceeding of the 5th AOTULE International Postgraduate Students Conference on Engineering, ISBN: 978-979-1344-91-3, pp. 154-157, 2010. 10. Yen K.S., Ratnam M.M., Akil H.M., “Measurement of flexural modulus of polymeric foam with improved accuracy using moire method”, Polymer Testing, Vol. 29, pp. 358-368, 2010.

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Thickness Effect on the Damage Mechanism in Stitched Carbon/Epoxy Composites containing Circular Holes Arief Yudhanto1, Naoyuki Watanabe1, Yutaka Iwahori2 Department of Aerospace Engineering, Tokyo Metropolitan University

Advanced Composite Technology Center, Japan Aerospace Exploration Agency

E-mail: arief-yudhanto@sd.tmu.ac.jp

Abstract This paper presents an experimental investigation of damage development in thin and thick stitched carbon/epoxy composites containing circular holes. Stitched composites are interruptedly tested under static tension at various stress levels. Damages at each stress level are examined using optical microscope. The damages are then classified, and the development of damage is tabulated. Results show that, in contrast to the behaviour of 2D composites, thicker stitched composites experience slower damage growth becaused delamination is impeded by stitch thread. The impediment of delamination is also responsible for the improvement of tensile strength when thickness is increased by 1.5 times.

1. Introduction Composite materials in this article refer to a macroscopic combination between continuous fibers and polymeric matrix. Fibers can be made of carbon, glass, boron or Kevlar®, whilst matrix can be available in the form of epoxy. Composites have been used in aerospace industry for more than four decades. The utilization is somewhat limited to secondary structures, e.g. vertical stabilizer, engine cowling. At present, composites are unprecendentedly used in primary structures, e.g. fuselage, wing. Airframe of Boeing 787 (Figure 1-a) consists of 50% composites1. The forthcoming Airbus 350XWB would contain composites of around 53%. Composites exhibit better strength-to-weight ratio compared to their metallic counterparts (aluminum alloy). The ‘light but strong’ property gives further financial benefit as the fuel consumption can be reduced when maximum take-off weight (MTOW) is reduced. However, upon

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loading, composites may suffer insidious damage so-called â&#x20AC;&#x2DC;delaminationâ&#x20AC;&#x2122; even below their ultimate strength. Delamination is defined as separation of two plies with dissimilar orientation (Figure 1-b), and this defect generally occurs in twodimensional (2D) composites, which are commonly used in aircraft. Delamination may cause significant reduction of fatigue strength, compressive strength and buckling loads in composites2.

Figure 1. (a) Boeing 787 uses 50% of composite materials for its airframe1, (b) Delamination in composite2

In order to improve delamination resistance, through-thickness reinforcement technique is employed. Stitching is one of the cost-efficient and most effective methods to improve delamination resistance. As shown in Figure 2, stitching involves an insertion of threads into a stack of preforms prior to resin infusion. Such through-thickness reinforcement is found to improve the interlaminar strength of composites3-11. Other techniques such as three-dimensional (3D) weaving may be as effective but the manufacturing setup time is unfavorable. However, stitching may deteriorate tensile stiffness of composites up to 20% compared to their unstitched composites12. The reason is that stitching could cause fiber misalignment, resin pocket and fiber breakage after needle penetration. Therefore, the use of stitched composite is still very limited due to those inevitable defects. Furthermore, the application of stitched composite in aircraft structures would be hampered by the fact that its open-hole mechanical performance has never been thouroughly studied. Open hole is required in aircraft structure in order to facilitate bolted joints and to allow access. Holes may accidently occur in irregular form, such as a result of high-velocity impact damage. Thus, effect of holes in composites should be studied, and it is imperative to evaluate the residual strength of composites

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with the presence of holes. The residual strength can be assessed by conducting open hole tension (OHT) test. Unfortunately, the investigation of OHT properties of stitched composites have been very few. Thuis and Bron of Nationaal Lucht- en Ruimtevaartlaboratorium (NLR, the Netherlands) revealed that stitching carbon/ epoxy composites with Kevlar速 thread with stitch density of 4/cm2 and 10/cm2 could reduce OHT strength by 4% and 56%, respectively13. In contrast, stitching was found to improve OHT strength under high temperature and high humidity14. Circular stitching with certain spacing and stitch pitch was found to improve OHT strength of composites because stitching can increase through-thickness fiber volume fraction, which in turn, assist the load transfer among plies15. However, a detailed account on the mechanism of strength reduction or improvement was not provided. In fact, the strength reduction/improvement can be studied by understanding the underlying damage development within composites. Present paper deals with the experimental investigation of damage mechanism in stitched carbon /epoxy composites containing circular hole. Effects of thickness on the damage development are assessed. Thickness effect is important because application of composites in aircraft structures frequently consider sizing aspects. Thick composites are often considered in the impact-prone regions16 whereby ultra-thick composites are also used as Side Stay Fitting (SSF) of the main landing gear17. However, 2D composites with a circular hole suffer strength reduction when ply-level up scaling is made. Increasing ply thickness of quasi-isotropic composites from 2 mm to 4 mm could reduce OHT strength by 42.8% for hole diameter of 6.35 mm18. The strength reduction is associated with the change of failure mechanism from pull-out to delamination. This is somewhat true because thicker composites tend to have lower delamination stress compared to thinner composites19. However, a detailed study on the OHT properties of thin and thick stitched composites has not been reported. It has some practical importance since the decision of utilizing stitched composites may be made, partially, based on the OHT characteristics and weight incurred due to thickness increase.

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Figure 2. Stitching method to improve delamination resistance

2. Experiments Composite materials used in present investigation are made of carbon T800SC-24K preforms (Toray Industries) and epoxy XNR/6813 resin. A stack of preforms with certain lay-up is stitched by Vectran速 thread with fiber linear mass density of 400 denier (0.044 gr/m, or 444 tex). Vectran is selected because it has better interlaminar fracture toughness compared to Carbon and Kevlar, whilst it also exhibits low moisture absorption23.Modified-lock stitch with stitch density of 11/cm2 (pitch = 3 mm, spacing = 3 mm) is adopted (Figure 3-a). Two types of composite were employed: thin composites with thickness of 4 mm (20-ply with stacking sequence of [+45/0/-45/902/+45/02/-45/90]s and thick composites with thickness of 6-mm (32-ply with stacking sequence of [+45/0/-45/902/+45/02/-45/902/+45/02/-45/90]s. The stitched composites manufactured by employing resin transfer molding (RTM) technique are provided by Toyota Engineering Corporation. Figure 3-b shows the lay-up of two specimens, whereby thick specimen is achieved by inserting sublaminate of (-45/902/+45/02) into the thin specimen. Fiber volume fraction Vf of stitched composites is estimated to be 58%.

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Figure 3. (a) Modified-lock stitch pattern, (b) Thin (4 mm) and thick (6 mm) stitched laminates

2.2. Test specimen preparation Test specimens are machined using diamond-coated wheel (AC400F) to achieve 200-mm long and 26-mm wide. Water spray is incorporated in the AC400F machine to reduce possible defects at the specimen edges during cutting. To make a hole, the center portion of coupon is tightly clamped using two composite plates with size of 50 mm x 26 mm to prevent chip out during drilling process. The hole with diameter of 6.35 mm is then created at the center of the specimen using a combination of drill-bit and reamer made of diamond-coated carbide (triple-angle drill). Microscopic observation is carried out after each drilling to ensure no pre-existing damage exists around the hole rims. Schematic picture of the specimen can be seen in Figure 4 (a) and (b). To measure the remote strain, uniaxial strain gages produced by Kyowa (gage length = 5 mm; gage factor = 2.09Âą1.0%) are used.

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Figure 4. (a) Specimen without hole, (b) Specimen with hole

2.3. Testing procedures Universal Testing Machine Instron 8802 with maximum capacity of 100 kN (tension) is used. Static tensile tests are performed by applying constant displacement with crosshead speed of 1 mm/min. Environmental setting is set at room temperature (RT) of 22°C. The procedure follows SACMA Recommended Method SRM 4R-94.

2.3.1 Tensile test The specimen is monotonically tensioned using Instron with crosshead speed of 1 mm/min. The load and displacement data is obtained from the machine, and stress – strain curves can be plotted. The stress is calculated by dividing the load with the gross area (width x thickness), i.e. hole diameter is omitted in the calculation. The strain is calculated by dividing the crosshead displacement with specimen’s length. From the curves, tensile strength (Su), failure strain (ef ), tensile stiffness (E ) and x Poisson’s ratio (nxy) can be obtained. ef is obtained as the corresponding strain at

which Su occurs. E and nxy were calculated at the linear region in the stress – strain x curve, that is between e = 0.1% and 0.3%.

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2.3.2 Open hole tension (OHT) test OHT test is carried out by monotonically loading the specimen with the rate of 1 mm/min. OHT strength (SOHT), E and nxy are obtained from the test. Three samples x are tested for each type of the specimens.

2.3.3 Interrupted Test interrupted test is carried out only for specimens with hole. It is performed by selecting stress level that may represent damage phase. In this experiment, four stress levels were selected: 50% (damage initiation); 80% (progressive damage); 95% (right before failure); and 100% (final failure) of SOHT. One specimen is tested for each stress level. After reaching a pre-determined stress level, the specimen is examined under optical microscope (Mitutoyo) with maximum magnification up to 50 times, and Olympus camera is used to capture the image. The interrogation areas are hole, free-edge and top surface (see Figure 5). In order to observe the damage in the hole area, cross-sectioning of specimen is carried out. Damage observation is performed only on one-half of the specimen with the assumptions that the damage is symmetrical. HOLE SURFACE

TOP SURFACE

FREE-EDGE SURFACE

Figure 5. Damage observation locations during interrupted test: hole surface, top surface and freeedge

3. Results and discussions 3.1 Tensile and OHT properties Figure 6 (a) shows typical tensile stress â&#x20AC;&#x201C; strain curves of Vectran-stitched carbon/ epoxy composites for specimens without hole. Non-linearity is observed in stress â&#x20AC;&#x201C; strain curve of thin composites (t = 4 mm) without hole after approximately 300 MPa. Thick specimen did not fail during the test because the specimen apparently had a higher failure load as compared to the capacity of the machine (maximum

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capacity is 100 kN). The non-linearity is not obvious in specimen with hole (Figure 6 (b)). Instead, some noticeable load drops are detected specifically between 300 and 500 MPa. Enlargement of stress – strain curves between 300 MPa and 500 MPa can be seen in Figure 6 (c). The load drops are indicated with the circles. Such load drops are also observed in 2D laminates18. As will be shown in damage analysis part, the load drop corresponds to the bundle delamination between +45° with 90° (or 0° plies) at the specimen edge.

Figure 6. Stress – strain curves for stitched carbon/epoxy (a) without hole, (b) with hole, (c) with hole and load drop area

Table 1 summarizes the mechanical properties of stitched composites with and without holes as inferred and calculated from the stress – strain curves in Figure 6 (a) and (b). Each value is an averaged value of three specimens. Thick composite, which is achieved by adding two sub-laminates of (-45/902/45/02) into 4 mm thin composite (equivalent with 1.5x thickness increase), exhibits 8% higher SOHT than thin composites. Compared to thick 2D composites, as shown in Figure 7, this strength increase is somewhat encouraging since usual 2D composites with ply-level scaling exhibits no improvement, or in some worst case, suffer strength reduction18. It was reported that SOHT reduction may reach up to 42.3% in 2D composites due to delamination. Strength improvement by increasing thickness in present stitched composites can be attributed to • The slower rate of damage formation in thick composites (major reason) • The fraction of load-bearing tows 0° bundles in thick composites, which is 31.25% as compared to 30% in thin composites (minor reason)

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Table 1. Tensile properties of stitched carbon/epoxy composites

Type

Thickness (mm) Hole dia. (mm)

Thin

6.35

Thick 6

6.35

Figure 7. Comparison of S

OHT

ef (%)

Ex (GPa)

nxy

752

1.63

50.4

0.35

485

0.99

47.1

0.26

Not failed

56.1

0.29

1.12

54.2

0.26

Strength (MPa)

Not failed 545

between stitched carbon composite (present) with unstitched

composite18

3.2. Failure modes Typical failure modes of specimen without hole and with hole can be seen in Figure 8 (a) and (b), respectively. Specimens without hole exhibits delamination failure, while specimen with hole displays pull-out, isolated failure. The failure in thin specimen without hole is characterized by separation of fiber tows, followed by separation between layers. To a certain extent, some stitches away from the fractured tows

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may still be intact, while other stitches near the fractured tows break, specifically at the stitch loop. Figure 8 (c) shows that stitches commonly break at the stitch loops. Under this circumstance, stitch loops appear to be one of the weakest links in stitched composites. Unfortunately, comparison can not be made with thick specimen without hole because the thick specimens did not reach final failure. Failure in thick and thin composites with hole exhibit similar pattern, that is isolated, pull-out failure. The bundle delamination would occur around the hole since the stresses around this area are significantly higher than the rest of the region19.

Figure 8. Typical final failure of stitched composites (a) specimen without hole, (b) specimen with hole, (c) failure around stitch loops

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3.3. Damage analysis in thin and thick composites As depicted in Figure 6 (c), several load drops are detected in the stress – strain curves of thin and thick stitch laminates containing holes. To investigate the ‘load drop’ phenomenon interrupted test is carried out by terminating applied load at prescribed stress levels (50%, 80%, 95% and 100% of SOHT. The microscopic observation is then performed on the specimens, specifically at the edge and hole rim. For the observation on the hole rim, cross-sectioning is done to the specimen by cutting the specimen into half. The identification of internal structures of composites20, which includes elliptical fiber bundles, resin channel, stitch yarns and fiber undulation, is performed using microscope. After the interrupted test, damage types found in the specimen are categorized. The categorization of damage in present paper can be regarded as an extension of a published report21. In that report, four damage types were found in cross-ply fabrics composites, namely longitudinal cracks, half cracks, whole cracks and double cracks. Those cracks were also found in stitched composites. In addition to those cracks, new types of damage were also discovered, namely interbundle crack, bundle delamination, bundle breakage, and tilde-shape (“~”) crack. Figure 9 shows the damage types found in stitched composites during interrupted test. Based on the damage category in Figure 9, qualitative observation of damage in thin and thick composites during interrupted test is tabulated in Table 2. It is clear that thick specimen is less sensitive to the damage formation compared to thin specimen, especially at the free-edge. As can be reviewed in [19], thick specimen has lower KT, and it manifests in higher SOHT compared to thin specimen. This consequently leads to a relatively slower damage formation in thick composite, especially at the free-edge.

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Figure 9. Damage types found in stitch composite: longitudinal crack, half crack, whole crack, double crack, interbundle crack, bundle delamination, bundle breakage, tilde crack

Table 2. Damage development in thin and thick stitched composites (E: edge; H: hole)

Damage type

Thin composite (t = 4 mm)

50%

80%

95%

100% 50%

80%

95%

100%

Longitudinal crack

Half crack

E, H

Whole crack

E, H

Double crack

Interbundle crack

E, H

Bundle delamination H

E, H

Bundle breakage

E, H

Thick composite (t = 6 mm)

Accompanying Table 2, stage-by-stage observation can be given herein: 50% SOHT

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No damage is found at the free-edge of thin and thick specimens. However, halfcrack and bundle delamination are found in the hole rim of both specimens. Halfcrack and whole-cracks occur mainly in off-axis bundles (e.g. 90°, 45°), while bundle delamination occurs between 45° and 0° bundles. Figure 10 shows, for instance, damage progression at applied stress of 50% and 80% of SOHT as observed using microscope in the hole rim. The damage progression can also be associated with the load drops shown in Figure 6 (c). In addition, tilde cracks are also found above resin pocket of stitch hole of both specimens. 80% SOHT Thin specimen exhibit more damage types compared to thick specimen. All types of damage are found at free-edge and hole rim of thin specimen, except bundle breakage. At this stage, the hole rim of thick specimen is occupied by half-cracks, whole cracks and bundle delamination. The interaction between two bundle delaminations drives the formation of interbundle cracks around the hole rim. Resin channel between two fiber tows may facilitate the formation of interbundle cracks. 95% SOHT There is similar damage types occurred at the free-edge of thin and thick specimens. However, the breakage of load-bearing bundle (0° bundle) starts to appear in thin specimen. The breakage generally resides near the resin channel between two fiber tows, or near the surface of specimen. The cause of fiber breakage is two-fold: (1) needle penetration during stitching process, or (2) very high interlaminar stresses at the edge. In thick specimen, only half-cracks and bundle delamination are found at the free-edge. It implies that thicker specimen has relatively lower interlaminar stresses at the edge. 100% SOHT (final failure) Both thin and thick specimens fail catastrophically. The typical failure as displayed in Figure 8 is delamination for thin specimen without holes, which is characterized by rupture of all 0° bundles, extensive transverse cracks, bundle separations and separation between plies. For specimens with hole, isolated pull-out mode takes place as the failure is mainly controlled by the high stress concentration factor. As a result, most of the damages in specimen with hole are intensified in the hole rim.

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Figure 10. Damage types found in thin (4 mm) and thick (6 mm) composites at 50% and 80% SOHT

The most critical damage types found in present experiment is fiber breakage, bundle delamination, half cracks and whole cracks. Half crack, and subsequently, whole cracks act as an initiator of bundle delamination. Bundle delamination is an isolated detachment between two fiber tows of dissimilar orientation. Once bundle delamination crosses over resin channel and connect with other isolated delamination, an extensive delamination appears in the specimen. At this stage, 0째 fibers would solely sustain all of the loads until final failure. It is also important to note that stitching creates inherent defects such as resin pocket (or resin channel) and in-plane and out-of-plane undulation. The former defect, i.e. resin pocket that is located on the surface of specimens, consequently triggers the formation of unique type of crack at the top and bottom surfaces of specimen, namely tilde crack. Some tilde cracks would appear above the resin pockets at around 50% SOHT. The size of tilde crack does not grow on the top surface, where bobbin stitches are located. Instead, its size may grow around the stitch loops, specifically at the bottom of specimen where needle threads are located. In practice, presence of tilde crack may affect the strain gage reading. When the strain gage is positioned above resin pocket, a location where this crack may potentially appear, the strain value may immediately increase especially at the edge of hole. Figure 11

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shows this phenomenon. Therefore, when strain gage is utilized, it is advisable to attach strain gage away from resin pocket. In present experiment, since the stitch spacing is 3.0 mm while the width of the strain gage is 2.5 mm, which is relatively wide for stitched composites, the interaction between resin pocket and strain gage is inevitable. In this case, strain measurement is therefore taken before the surface crack is developed, e.g. around 100 MPa.

Figure 11. The disruption of strain reading using strain gages as a result of tilde crack on the surface of stitched composite appears after 200 MPa

4. Conclusions Experimental investigation of damage progression in thin and thick stitched carbon/ epoxy composites containing circular holes is performed. Stitched carbon/epoxy composite is subjected to static tension interruptedly at various stress levels. The damages appeared at the hole and edges are classified, and the development of damage is summarized. Several conclusions can be drawn from the experiments: â&#x20AC;˘ Contrary to the trend in unstitched composites, increasing thickness by 1.5 in stitch composite would result in 8% higher SOHT â&#x20AC;˘ This is due to the fact that thick stitched composite experiences slower damage growth as compared to the thin stitched composites. Delamination, in this regard,

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is impeded by the presence of stitches. • Eight damage types in stitched composites have been found: longitudinal cracks, half cracks, whole cracks, double cracks, interbundle crack, bundle delamination, bundle breakage, and “~” sign-like (tilde or diacritical) crack • Resin pocket, which is induced by stitching process, facilitates the development of interbundle cracks. Interbundle crack may accelerate the formation of delamination. • Stitching enables part-through crack (tilde “~” crack) to form on the back surface of stitched composites. Tilde crack may disrupt strain reading using strain gages, specifically below 200 MPa. It is advisable to use non-contact strain measurement technique when strain mapping up to final failure is a necessity.

Acknowledgement Authors gratefully acknowledge Tokyo Metropolitan Government (Asian Network of Major Cities 21 or ANMC21) for the financial support.

Referensi 1. Dodt, T. Introducing the 787: Effect of Major Investigations and Interesting Tidbits. International Society of Air Safety Investigators Forum, September 2011. 2. Sridharan S (Ed.). Delamination behaviour of composites. Woodhead Publishing Ltd., 2008. 3. Tong L, Mouritz AP, Bannister MK. 3D fibre reinforced polymer composites. Elsevier Ltd., 2002; 182 – 195. 4. Dransfield KA, Baillie CA, Mai YW. Improving the delamination resistance by stitching – a review. Composites Sci Tech 1994; 50: 305 – 317. 5. Cox BN, Massabo R, Kedward KT. The suppression of delaminations in curved structures by stitching. Composites Part A 1996; 27: 1133 – 1138. 6. Jain LK, Mai YW. Recent work on stitching of laminated composites – theoretical analysis and experiments. Proc. 11th Int Conf Composites Mat’l, 14 – 18 July 1997; I-25 – I-21. 7. Mouritz AP, Jain LK. Interlaminar fracture properties of stitched fiberglass composites. Proc. 11th Int Conf Composites Mat’l, 14 – 18 July 1997; V-116 – V-127. 8. Jain LK, Dransfield KA, Mai YW. On the effects of stitching on CFRPs – II. Mode II delamination toughness. Composites Sci Tech 1998; 59: 829 – 837. 9. Mouritz AP, Jain LK. Further validation of the Jain – Mai models for interlaminar

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fracture of stitched composites. Composites Sci Tech 1999; 59: 1653 – 1662. 10. Iwahori Y, Nakane K, Watanabe N. DCB test simulation of stitched CFRP laminates using interlaminar tension test results. Composites Sci Tech 2009; 69: 2315 – 2322. 11. Tan KT, Watanabe N, Sano M, Iwahori Y, Hoshi H. Interlaminar fracture toughness of Vectran-stitched composites – experimental and computational analysis. J. Composites Matl 2010, doi: 10.1177/0021998310369581. 12. Mouritz AP, Cox BN. A mechanistic interpretation of the comparative in-plane mechanical properties of 3D woven, stitched and pinned composites. Composites Part A 2010; 41: 709 – 728. 13. Thuis HGSJ, Bron E. The effect of stitching density and laminate lay-up on the mechanical properties of stitched carbon fabrics. CR-96126-L, National Aerospace Laboratory (NLR), the Netherlands, 1996. 14. Chen G, Cheng X, Li Z, Kou C. The effect of environment on tensile properties of stitched and unstitched laminates (with a hole). J. Reinf. Plastics Comp, 2005. Vol. 24, 17: 1883 – 1889. 15. Han XP, Li LX, Zhu XP, Yue ZF. Experimental study on the stitching reinforcement of composite laminates with a circular hole. Composites Sci Tech 2008; 68: 1649 – 1653. 16. Naik NK, Doshi AV. Ballistic impact behaviour of thick composites: Parametric studies. Composite Struct 2008, 82:447-464. 17. Zimmerman K, Zenkert D, Siemetzki M. Testing and analysis of ultra thick composites. Composites Part B 2010, 41:326-336. 18. Green BG, Wisnom MR, Hallett SR. An experimental investigation into the tensile strength scaling of notched composites. Composites Part A 2007; 38: 867 – 878. 19. Yudhanto A, Watanabe N, Iwahori Y, Hoshi H. In-plane mechanical characteristics of stitched fabrics with and without holes. Proc. 14th European Conf Comp Mat’l, 7 – 10 June 2010, Budapest, Hungary; 962-ECCM14. 20. Mattsson D, Joffe R, Varna J. Methodology for characterization of internal structure parameters governing performance in NCF composites. Composites Part B, 2007; 38: 44 – 57. 21. Edgren F, Mattsson D, Asp LE, Varna J. Formation of damage and its effects on non-crimp fabric reinforced composites loaded in tension. Composites Sci Tech 2004; 64: 675 – 692.

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Monitoring Secondary Bending Failure of Bonded Composite Panels under Tension Load using Fiber Bragg Grating (FBG) Sensors A Trilaksono1, N Watanabe1, H Hoshi1, S Takeda2, Y Iwahori2. 1

Department of Aerospace Engineering, Tokyo Metropolitan University,

Advanced Composite Technology Center, Japan Aerospace Exploration Agency

E-mail: trilaksono-agus@sd.tmu.ac.jp

Abstract This paper presents an experimental investigation for monitoring the secondary bending failure of bonded composite panels under tension load using Fiber Bragg Grating sensors. For a better understanding, the numerical formulation and simulation of secondary bending phenomenon are also shown. A simple beam bonded with smaller plate is used as skin-stiffened model of aircraft structure. Those plates are bonded by adhesive bonding and subjected to uniaxial tension loading. Relationships between normalized intensity and normalized wavelength to the inplane displacement during uniaxial tension test are provided as the results of the experiment. Keywords: secondary bending, fiber bragg grating, damage mechanism ©2011. Persatuan Pelajar Indonesia Jepang. All rights reserved.

1. Introduction ‘Integrated’ and ‘lightweight’ are two important keywords in structural health monitoring of composite elements for the application in aircraft structures. In aircraft structure, one of the important elements is skin stringer. Upon loading, for instance uniaxial tension, skin stringer may experience a phenomenon called ‘secondary bending’. Secondary bending creates peeling failure at the interface between skin and stringers. This type of failure is critical for the integrity of aircraft structures. However, it is difficult to detect using conventional method such as strain gage because the failure is insidious within a structure. The objective of present research is to monitor secondary peeling phenomenon in

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the skin stringers using an optical fiber, namely Fiber Bragg Grating (FBG) sensor. Skin stringer is simplified in the form of skin-stiffened specimen, and the specimen is subjected to static tension.

2. Principle of Fiber Bragg Grating (FBG) Sensor Fresnel reflection is the basic principle in the operation of FBG. Bragg wavelength or reflected wavelength (lB) is defined by the following relationship (1)

where l is the effective refractive index of the grating in the fiber core and

lB = 2P

is the

grating period1.

3. Secondary Bending Phenomenon Knowledge of stresses at the most critical part of aircraft structure is essential. For example, hub stresses in the fuselage structure are transferred from one skin panel to the adjacent panel via bonded and/or riveted joints. The stress is not collinear through the joint but offset or eccentric. The secondary bending is highly dependent on the magnitude of the eccentricity and the flexural rigidity of the joint. Figure 1 shows the secondary bending phenomenon in simple beam bonded with smaller plate subjected to uniaxial tension.

New Neutral Axis

P Moment = P.w

tstiffener

tskin

Neutral Axis

Figure 1. Secondary bending phenomenon

Figure 1. Secondary bending phenomena 2,3

The The equation of secondary bending phenomenon can becan derived using Euler . For a equation of secondary bending phenomenon be derived using formulation Euler distance m ď&#x201A;Ł x 2,3 ď&#x201A;ł ď&#x201A;Ľ, and based on the coordinates and signs convention in Figure 1, the governing formulation . For a distance m < x < , and based on the coordinates and signs differential equation for the coordinate y in the displaced configuration is: M

(đ??¸đ??ź)ďż˝ďż˝ďż˝ďż˝

ďż˝ ďż˝ đ?&#x2018;Śďż˝ďż˝ďż˝ďż˝ ďż˝ďż˝ ďż˝

= Pđ?&#x2018;¤ďż˝ďż˝ďż˝ďż˝

where bending stiffness (EI) of skin is given as follows ďż˝

(1)

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convention in Figure 1, the governing differential equation for the coordinate y in the displaced configuration is: M

(EI)skin

d2 yskin

= Pwskin dx2

(1)

where bending stiffness (EI) of skin is given as follows

(EI)skin = Eskin tskin3 12 (1- v2)

(2)

Assumed that hskin =

P √ (EI) skin

Eq. (1) becomes

yskin = Hskin e{-hskin (x-m)} + H'skin e{hskin (x-m)}

(3)

H and H’ are coefficients in secondary bending moment. The boundary condition is as follows yskin = 0 at x =

, whilst H’skin = 0. M Bending moment at x = m is Mskin and Hskin = skin P

For 0 < x <

, the governing differential equation for the coordinate y in deformed

configuration is d2 ystiffener

= (EI)stiffener where,

(EI)stiffener =

dx2

Eskin 3 (1- v2)

= Pystiffener

{(tskin - y0)3 + y03 }+

Estiffener 3 (1- v2)

(4)

{(tskin + tstiffener - y0)3 – (tskin - y0)3}

(5)

and y0=

Eskin t2skin +Estiffener tstiffener {(tskin+ tstiffener )2- t2stiffener ) (Eskin tskin+ Estiffener tstiffener )

Using

hskin

(6)

P , Eq. (4) becomes (EI) √ stiffener

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ystiffener = Hstiffener

e(-hstiffener x) + H’stiffener e(hstiffener x)

(7)

Hskin = H’stiffener

(8)

dystiffener

Using the boundary condition of

= 0 at x = 0, then:

Let M = Mskin at x = m then we obtain following relationship: Mstiffener

Hstiffener =

2Pcosh(hstiffener m)

Compatibility at x = m gives

Mskin =

hstiffener hskin

dyskin dx

dystiffener dx

(9)

then

Mstiffener tanh(hstiffener m)

(10)

Compatibility at x = m gives the following ystiffener - yskin = w, then Mstiffener = Pw+Mskin

(11)

Substituting Eq. (11) into (10) yield unknown coefficients of Mstiffener =

hskinPw hskin + hstiffener tanh(hstiffener m)

(12)

Bending stress at x = m is σ(x=m) = ± 1 Mstiffener t_stiffener

Istiffener

(13)

with Istiffener = 1 t3stiffener then 12 σ(x=m) = ±

6 hskinPw

hskin + hstiffener tanh(hstiffener m) t2stiffener

From equations above, it can be explained that the total operational stress during aircraft flight in the joint is the membrane stress and the secondary bending stress. Or, in simple formulation it can be expressed as follows:

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σOperational =σApplied load + σSecondary bending load

4. Materials and Experiments Unidirectional carbon/epoxy composite system of IMS60/#133 was used. The composite plate with 8-ply of [0/0/+45/-45]s was fabricated using autoclave at ±180°C. The plate was cut to produce a ‘skin’ specimen with following dimension: 250 mm (length) x 25 mm (width). The ‘skin’ specimen was patched using a smaller plate (‘stiffener’) made of the same material. The bonding process was performed using off-white adhesive DP420 by 3M. Prior to bonding process, FBG sensor was embedded between the skin and the stiffener. The location of FBG sensor was near the edge of specimen, where the most potential failure would occur. FBG sensor was provided by Fujikura Fiber Optic with Ø 125mm diameter. Grating span of the FBG sensor is 15 mm. Tensile test was conducted using Universal Testing Machine Instron 8802. Cross-head speed was 0.5 mm/min. Non-contact strain measurement, advanced video extensometer (AVE), was used to monitor axial strain on the back side of the stiffener to clarify how secondary bending might occur during tensile test. During tensile test, optical fiber was concurrently lighted using broadband light source (ASE FL7002, 1530-1610 nm made by FiberLabs). Spectrum reflection was measured using optical spectrum analyzer (MS9710C by Anritsu Co). The reflection was continuously measured until the specimen breaks.

5. Results and Discussion Figure 2 (a) shows the relationship between normalized intensity (I/I0) and displacement (dashed line), as well as load – displacement curve (solid line). Figure 2 (b) shows similar plot except that the y-axis on the left-hand side is normalized wavelength (l/l0). The load was basically borne by the adhesive. Once the load reached the peak, the severe peeling damage occurred. After the peak has been reached, the load became relatively constant and followed ‘plateau’ trend until the specimen broke. It can be seen from Figure 2 (a) and (b) that the shape of spectrum (relationship between power in dB and wavelength in nanometer scale) at three points could indicate the occurrence of damage. The change of spectrum width may indicate that the damage occurred.

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(a)

(b) Figure 2. Relationship between normalized intensity and normalized wavelength during uniaxial tension of â&#x20AC;&#x2DC;skin-stiffenedâ&#x20AC;&#x2122; specimen

6. Conclusion Monitoring damage due to secondary bending phenomenon using FBG has a great potential because damage may initiate even under a relatively small load. FBG is also useful because detection can be made in-situ, in which other devices may not be capable of doing so because accessibility is very limited.

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References 1. Takeda S, Okabe Y, Yamamoto T, Takeda N. Detection of edge Delamination in CFRP Laminates under Cyclic Loading Using Small-Diameter FBG Sensors. Composite Science and Technology 2003; 6: 1885-1894. 2. Gere JM, Timoshenko SP. Mechanics of Materials. Third SI Edition Chapman & Hall, London, 1991. 3. Schijve, J. Secondary Bending Moment. NLR 72036U, 1972.

vol.19 no.3

TEKNOLOGI Optimasi Pembuatan Pulp Serabut Sawit (Elais guineensis) melalui Proses Hidrolisis dengan NaOH Andrian Wahyu Jati1, Nela Agustin K2, Exsien Setyorini1 Jurusan Teknologi Industri Pertanian, Universitas Brawijaya

Jurusan Teknologi Hasil Pertanian, Universitas Brawijaya

Email: andrianjati@gmail.com

Abstrak Serabut sawit merupakan limbah yang dihasilkan industri minyak kelapa sawit. Pada tahun 2008 jumlah serabut sawit mencapai 2 juta ton dan belum termanfaatkan. Kandungan selulosa sekitar 44,14% dalam serabut sawit dapat dimanfaatkan sebagai bahan pembuatan kertas melalui proses delignifikasi. Penelitian dilakukan menggunakan metode Respon Permukaan dengan Rancangan Komposit Terpusat. Faktor yang diteliti pada adalah konsentrasi NaOH (X1) dan lama pemasakan (X2). Faktor digunakan untuk Rancangan Komposit Pusat, yaitu konsentrasi NaOH 10, 12, dan 14%, serta lama pemasakan 60, 80, dan 100 menit. Hasil perlakuan optimal pada persentase larutan NaOH 7% sebanyak 11,09% (v/v) dan lama pemasakan selama 67,84 menit dengan nilai indeks tarik 44,1129 Nm/g dan indeks sobek 17,6678 mNm2/g. Karakteristik fisik dan kimia pulp serabut sawit antara lain rendemen 41,95%, gramatur 125,33 g/m2, ketebalan 0,213 mm dan kadar air 7,26%.

Kata kunci: Optimasi, pulp, serabut sawit, NaOH

1. PENDAHULUAN Saat ini, tingkat kerusakan hutan di Indonesia sudah pada tingkat yang mengkhawatirkan. Berdasarkan State of the Worldâ&#x20AC;&#x2122;s Forests 2007 yang dikeluarkan The UN Food & Agriculture Organization (FAO), kerusakan hutan di Indonesia pada periode 2000-2005 mencapai 1,8 juta hektar/tahun. Laju kerusakan hutan di Indonesia ini membuat Guiness Book of The Record memberikan â&#x20AC;&#x2DC;gelar kehormatanâ&#x20AC;&#x2122; bagi Indonesia sebagai negara dengan daya rusak hutan tercepat di dunia. Tingginya tingkat kerusakan hutan diakibatkan oleh banyaknya industri yang menggunakan kayu-kayu hutan sebagai bahan baku utama, salah satunya adalah

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industri kertas. Berdasarkan data Badan Pusat Statistik tahun 2006 menunjukkan bahwa tingkat konsumsi kertas mencapai 5,96 ton per tahun. Meski tidak secara langsung, tingginya tingkat konsumsi kertas menjadi pemicu maraknya pembalakan liar di Indonesia. Upaya untuk mengurangi penggunaan kayu hutan sebagai bahan baku kertas adalah dengan memanfaatkan bahan lain, salah satunya adalah serabut sawit. Serabut sawit merupakan hasil samping dari pengolahan kelapa sawit yang dipisahkan dari buah setelah pengutipan minyak dan biji dalam proses pemerasan. Berdasarkan data Badan Pusat Statistik Indonesia, pada tahun 2004 total limbah serabut sawit yang dihasilkan di Indonesia mencapai 1,18 juta ton per tahun. Komposisi serabut sawit dalam tandan buah sawit mencapai 12% dengan kandungan selulosa 44,14%; hemiselulosa 19,28% dan lignin 16,19%1. Tingginya kandungan selulosa dalam serabut sawit memberikan peluang yang sangat besar untuk diolah sebagai bahan pembuatan pulp. Pulp merupakan bubur kertas yang berasal dari hasil pemisahan serat dari bahan berserat baik kayu maupun non kayu yang melalui beberapa proses pembuatan. Bahan yang dibutuhkan pada proses pembuatan pulp adalah selulosa yang sudah terpisah dengan komponen lainnya seperti lignin. Keberadaan lignin pada proses pulping dapat mengurangi kualitas kertas yang dihasilkan serta mengubah warna kertas. Lignin yang terdapat pada sumber serat akan mengalami pelunakan menjadi fragmen-fragmen kuat oleh ion hidroksil (OH) larutan pemasak2. Pada pembuatan kertas dari serabut sawit belum diketahui konsentrasi NaOH yang harus ditambahkan serta lama waktu pemasakan. Pada penelitian ini akan dicari hubungan antara konsentrasi NaOH yang digunakan serta lama pemasakan pulp. Penggunaan NaOH dan lama pemasakan yang optimum terhadap serat sawit dilakukan dengan cara mengamati sifat fisik dan mengukur rendemen serat pulp. Hasil penelitian diharapkan dapat diperoleh suatu kondisi proses yang optimum untuk menghasilkan pulp yang berkualitas sehingga dapat menjadi alternatif pemanfaatan limbah serabut kelapa sawit dan alternatif bahan baku industri kertas untuk mengurangi eksploitasi kayu hutan.

2. METODE OPTIMASI Rancangan penelitian yang digunakan dalam metode respon permukaan adalah Rancangan Komposit Terpusat (Centralized Composite Design) dengan menggunakan dua faktor yaitu prosentase penambahan bahan pelarut NaOH

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dan waktu pemasakan. Sesuai dengan metode Respon Permukaan 2 faktor maka pengulangan dilakukan pada titik tengah (X=0) sebanyak 5 kali. Pada prosentase larutan NaOH 7% sebanyak 12% v/v (X1=0) dan lama pemasakan 80 menit (X2=0). Nilai Îą dipilih k=2 adalah 2k/4 = 22/4 = 1.414. Tabel 1. Rancangan Percobaan Komposit Terpusat

Variabel Kode

Variabel Asli

NaOH (%)

Waktu Pemasakan (menit)

Respon

Indeks Tarik (Nm/g)

IndeksSobek (mN.m2/g)

-1

100

-1

100

-1.414 0

9,172

1.414 0

14,828

-1.414 12

51,72

1.414 12

108,28

3. PEMBUATAN PULP SERABUT SAWIT Proses pembuatan pulp diawali dengan proses penimbangan dan pencucian, dimana untuk tiap sampel digunakan 50 gram serabut sawit. Selanjutnya serabut sawit dihidrolisis ditambah dengan NaOH 7% sejumlah perlakuan yang diberikan seperti pada Tabel 1. Setelah bubur terbentuk, pulp kemudian diputihkan menggunakan hydrogen peroksida sebanyak 10%. Tahapan terakhir yaitu dengan mencetak pulp menjadi lembaran pulp dengan menggunakan screen 180 mesh.

4. ANALISA HASIL PENELITIAN Penelitian terhadap pulp dilakukan untuk menganalisis atau mempelajari hasil yang telah dicapai setelah diperoleh titik optimal terhadap gramatur, rendemen, pH, dan uji fisik yang meliputi Elmendorf Tearing Test (Uji Ketahanan Sobek), Thickness Test (Uji ketebalan) dan Paper Tensile Strenght Test (Uji Ketahanan Tarik). Pengolahan

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data menggunakan program Design-Expert 8.0.4 yang diperoleh dari www.statease. com.

5. ANALISA HIDROLISIS SERABUT SAWIT Serabut sawit (Elais guineensis) merupakan serat yang dihasilkan dari limbah pengolahan minyak sawit. Kandungan serat kasar yang mencapai 40,80% terbukti dapat dimanfaatkan sebagai bahan pembuatan pulp kertas. Untuk menghasilkan pulp dari serabut sawit diperlukan proses hidrolisis. Proses hidrolisis atau delignifikasi lignin dapat dilakukan menggunakan NaOH 0.25 N sebanyak 10-20%3. Sedangkan untuk proses hidrolisis serat palmyra palm oil dapat dilakukan menggunakan NaOH 5-10% atau dengan menggunakan HCl 5-10%4. Pulp yang dihasilkan dari serabut sawit menggunakan NaOH 0.25 N ataupun HCl 1N sebanyak 10-20% kurang optimal. Hal tersebut dapat dilihat melalui karakteristik pulp yang masih kasar dan tidak bisa dihancurkan. Oleh karena itu, teori yang dikemukakan tidak sesuai ketika diterapkan pada serabut sawit.

Gambar 1. Pulp Serabut Sawit

Gambar 1 merupakan pulp serabut sawit dengan kondisi optimal, dimana proses hidrolisis serabut sawit didapatkan dengan mengkombinasikan proses pemasakan menggunakan NaOH 10-14% dengan HCl 10%. Dengan fakta tersebut telah membuktikan bahwa serabut sawit dapat dimanfaatkan sebagai bahan baku pembuatan pulp.

6. ANALISA RESPON INDEKS TARIK DAN SOBEK Nilai Indeks Tarik dan Indeks sobek lembaran pulp dapat diketahui dengan menghitung kekuatan tarik dan kekuatan sobek lembaran pulp kemudian dibagi dengan gramatur lembaran Tabel 2.

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Tabel 2. Nilai Indeks Tarik dan Indeks Sobek Lembaran Pulp

NaOH

Waktu

Kuat Tarik

(%)

(menit)

(gr/m )(mN)

3920

823.20

37.69

7,92

100

6710

1409.10

42.47

8,92

5300

1113.00

43.44

9,12

100

2010

422.10

20.79

4,37

3510

1572.48

46.18

20,69

4920

2204.16

43.93

19,68

3910

1751.68

44.94

20,13

3760

1684.48

44.76

20,05

3750

1680.00

45.73

20,49

9,172

3390

1115.31

35.31

11,62

14,828

1870

615.23

22.80

7,50

51,72

3980

1309.42

38.76

12,75

108,28

3480

1144.92

35.63

11,72

Kuat Sobek (Nm/g)

Indeks Tarik

Indeks Sobek

(mNm /g) 2

Berdasarkan hasil analisa data dengan menggunakan metode respon permukaan (Tabel 2) diperoleh nilai indeks tarik pulp terbesar adalah 46,18 Nm/gr yang diperoleh dari perlakuan NaOH 7% dengan presentase 12% (v/v) dan lama pemasakan 80 menit. Indeks tarik terkecil adalah 20.79 Nm/gr yang diperoleh dari perlakuan NaOH 7% dengan persentase 14% (v/v) dan lama pemasakan 100 menit. Indeks sobek diperoleh hasil terbesar 20.69 mN.m2/gr yang diperoleh dari perlakuan NaOH 7% N dengan persentase 12 % (v/v) dan lama pemasakan 80 menit. Indeks sobek terkecil adalah 4.37 mN.m2/gr yang diperoleh dari perlakuan NaOH 7% N dengan persentase 14% (v/v) dengan lama pemasakan 100 menit. Berdasarkan kurva respon permukaan indeks tarik Gambar 2(a) dan indeks sobek Gambar 2(b) terlihat bahwa penambahan larutan NaOH dan lama pemasakan memiliki nilai yang berbeda nyata. Hal tersebut disebabkan karena respon yang terbentuk antara rasio NaOH (A) dan lama pemasakan (B) secara parsial maupun ortogonal adalah dalam bentuk kuadrat (lengkung). Dengan demikian dapat diartikan bahwa model kuadratik merupakan model yang tepat dalam memberikan pengaruh yang signifikan terhadap respon indeks tarik dan indeks sobek.

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(a)

(b)

Gambar 2. Kurva permukaan respon hubungan NaOH dan lama pemasakan terhadap respon (a) Indeks Tarik dan (b) Indeks Sobek .

Berdasarkan kurva permukaan respon indeks tarik dan indeks sobek pada Gambar 2 (a) dan (b) menunjukkan hubungan antara NaOH dengan lama waktu pemasakan. Hubungan ini menunjukkan bahwa semakin tinggi konsentrasi NaOH dan lama waktu pemasakan akan menghasilkan indeks tarik dan indeks sobek yang semakin tinggi. Akan tetapi indeks tarik dan indeks sobek mengalami penurunan ketika NaOH yang ditambahkan terlalu banyak dan waktu pemasakan terlalu lama.

7. OPTIMASI RESPON INDEKS TARIK DAN SOBEK Perhitungan optimasi dilakukan dengan batasan-batasan yang dilakukan sesuai dengan tujuan yang diharapkan. Tujuan dari optimasi ini adalah untuk memaksimalkan nilai respon indeks tarik dan indeks sobek dengan meminimalkan penambahan NaOH dan lama pemasakan. Tingkat kepentingan untuk indeks tarik, indeks sobek, NaOH, dan waktu pemasakan adalah sama yaitu 3 menit. Persamaan yang digunakan dalam analisis adalah persamaan dalam bentuk kode sebagai berikut: T = -396,72290 +55,31389X + 3,20325Y – 0,17144XY-1,82084X2 - 0,008033Y2…. (1) S = -303,32426 +39,21734X + 2,32425Y – 0,03587XY-1,53834X2 - 0,012040Y2 ….(2)

Keterangan:

T = Indeks Tarik

X = Konsentrasi NaOH

S = Indeks Sobek

Y = Lama Waktu Pemasakan

Berdasarkan persamaan model indeks tarik (Persamaan 1) dapat diketahui bahwa koefisien X2 (-1,8204) lebih kecil dibandingkan koefisien Y2 (-0,008033). Sehingga dapat dikatakan bahwa konsentrasi NaOH berpengaruh lebih besar daripada lama pemasakan terhadap indeks tarik. Indeks sobek kertas juga lebih dipengaruhi oleh

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konsentrasi NaOH daripada lama pemasakan dikarenakan koefisien X2 (-1,53834) lebih kecil daripada koefisien Y2 (-0,012040). Hal tersebut dikarenakan semakin kecil nilai probabilitas suatu model, maka model tersebut memiliki pengaruh yang semakin besar. Tabel 3. Solusi Hasil Komputasi Design-Expert 8.0.4

NaOH

Waktu

Indeks Tarik

Indeks Sobek

(%)

(menit)

(Nm/g)

(mN.m2/g)

11.09

67.84

44.1129

Ketepatan

17.6678

0.814

Keterangan Terpilih

Dari Tabel 3 terdapat satu solusi optimal yang memiliki nilai ketepatan sebesar 0,814. Fungsi ketepatan adalah untuk menentukan derajat ketepatan hasil solusi optimal5. Dimana semakin mendekati satu semakin tinggi nilai ketepatan optimasinya. Dalam optimasi yang dilakukan diperoleh nilai ketepatan 0,814 atau dapat dikatakan bahwa tingkat ketepatan optimasi sebesar 81,40%. Tabel 4. Hasil Prediksi Solusi Optimal Persentase NaOH 11,09% dan Lama Pemasakan 67.84 menit.

Respon

Prediksi

SE Pred 95%

PI low 95%

PI high

Indeks tarik

44.19

2.743

37.6226

50.5954

Indeks sobek 17.66

2.03524

12.854

22.4792

Dari Tabel 4 dapat diketahui bahwa standar kemungkinan nilai terendah untuk indeks tarik adalah 37.6226 Nm/g dan indeks sobek adalah 12.854 mNm2/g. Kemudian untuk nilai tertinggi indeks tarik adalah 50.5954 Nm/g dan kekuatan sobek adalah 22.4792 mNm2/g. Hasil yang didapat pada model terhadap respon kekuatan tarik dari perlakuan persentase NaOH 7% sebanyak 11,09% (v/v) dengan lama pemasakan 67.84 menit mencapai nilai indeks tarik sebesar 44.1129Nm/g dan nilai indeks sobek sebesar 17.6678 mNm2/g.

8. ANALISA HASIL PERLAKUAN TERPILIH Analisa hasil perlakuan terpilih yaitu pada persentase NaOH 7% sebanyak 11,09% dan lama pemasakan selama 67,84 menit dapat dilihat pada Tabel 5

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Tabel 5. Analisa Fisik Lembaran Pulp pada Perlakuan Terpilih

Analisa

Nilai

Rendemen (%)

41.95

Kadar Air (%)

7.26

Gramatur (g/m2)

125.33

Ketebalan (mm)

0.213

Indeks Tarik (Nm/g)

44.1129

Indeks Sobek (mNm /g)

17.6678

Indeks tarik pada perlakuan terpilih sebesar 44,1129 Nm/g. Beberapa faktor yang juga mempengaruhi indeks tarik pada lembaran pulp serabut sawit antara lain arah serat yang dalam penelitian ini bersifat kurang teratur dan jumlah serat yang terdapat dalam pulp. Indeks sobek pada perlakuan terpilih sebesar 17,6678 mNm2/g. Tingginya nilai indeks tarik pada lembaran pulp serabut sawit disebabkan oleh panjang serat yang Nampak pada lembaran. Hal ini seperti diungkapkan melalui penelitian Seth dan Dage yang menjelaskan bahwa pada lembaran yang mempunyai ikatan serat yang lemah, ketahanan sobeknya lebih tergantung pada panjang serat daripada kekuatan serat, tetapi keadaan yang sebaliknya terjadi pada lembaran yang memiliki ikatan serat yang baik6. Pengukuran ketebalan lembaran pulp dilakukan pada empat titik yang berbeda. Hal ini disebabkan karena satu lembar pulp yang dihasilkan mempunyai ketebalan yang tidak merata. Kereagaman ketebalan, gramatur dan rapat massa memiliki implikasi yang sangat erat satu sama lain. Rapat massa merupakan perbandingan gramatur dengan ketebalan7. Ketebalan pulp dari serabut sawit ini adalah 0,213 mm.

9. PERBANDINGAN PULP SERABUT SAWIT DENGAN BAHAN LAIN Untuk mengetahui kualitas lembaran pulp dari serabut sawit yang dihasilkan perlu dilakukan perbandingan dengan hasil dari penelitian tentang pembuatan kertas dari bahan yang lain. Kertas dari serabut sawit yang dihasilkan dibandingkan dengan kertas dari jerami padi, akasia, batang pisang, batang kelapa sawit dan serat buah palmyra palm dapat dilihat pada Tabel 6.

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Tabel 6. Perbandingan Kertas Serabut Sawit dengan Kertas Lain

Jenis Bahan

Rendemen

Gramatur

Indeks Tarik

Indeks Sobek

(gr/m2)

(Nm/g)

(mN.m /g)

35,40%

200

40.00

8.20

13.80

1.12

Jerami Padi 8

Serat buah palmyra palm

40,70%

Batang Kelapa Sawit 9

121.25

15.58

17.22

Akasia

51,64%

57.63

7.31

Serat Batang Pisang 11

34,00%

71.8

33.52

13.78

Serabut Sawit

41,95%

125.33

44.11

17.67

Pada Tabel 6 ditampilkan data rendemen, gramatur, indeks tarik, dan indeks sobek kertas dari jerami padi, akasia, batang pisang, batang kelapa sawit, serat buah palmyra palm dan serabut sawit. Data tersebut dapat menunjukkan dimana posisi kertas dari serabut sawit dibanding dengan kertas dari bahan lain. Lembaran pulp serabut sawit mempunyai rendemen sebesar 41,95% yang nilainya berada di bawah rendemen kertas dari akasia yang mencapai 51,64%. Nilai rendemen pada suatu proses produksi berpengaruh terhadap tingkat keuntungan ataupun hasil yang diperoleh apabila dikembangkan dalam skala industri. Semakin besar rendemen yang dihasilkan akan memberikan nilai keuntungan yang semakin tinggi pada suatu proses produksi. Nilai gramatur yang dimiliki oleh kertas yang dihasilkan dari tiap bahan tersebut. Dari data tersebut dapat dilihat bahwa kertas serabut sawit mempunyai nilai gramatur sebesar 125,33 gr/m2. Nilai tersebut masih berada di bawah gramatur kertas dari jerami padi yang mencapai 200 gr/m2. Nilai indeks tarik lembaran pulp dari serabut sawit sebesar 44,11 Nm/g yang nilainya berada dibawah kertas dari akasia yang mencapai 57,63 Nm/g. Sedangkan nilai indeks sobek lembaran pulp serabut sawit mempunyai nilai sebesar 17,67 mNm2/g yang merupakan nilai terbesar dari pulp lain yang dibandingkan

vol.19 no.3

10. KESIMPULAN 1) Serabut sawit dapat dimanfaatkan sebagai bahan baku pembuatan kertas melalui proses delignifikasi lignin menggunakan NaOH 7% dan dilanjutkan dengan HCl 1N. 2) Penambahan konsentrasi NaOH dan waktu pemasakan berpengaruh nyata terhadap lembaran pulp yang dihasilkan. 3) Pengaruh persentase NaOH (X) dan waktu pemasakan (Y) terhadap respon indeks tarik (T) dan indeks sobek (S) sesuai dengan nilai koefisien dari model persamaan kuadratik, T = -396.72290 +55.31389X + 3.20325Y â&#x20AC;&#x201C; 0.17144XY-1.82084X2 - 0.008033Y2 S = -303.32426 +39.21734X + 2.32425Y â&#x20AC;&#x201C; 0.03587XY-1.53834X2 - 0.012040Y2 4) Hasil perlakuan terpilih pada persentase larutan NaOH 7% sebanyak 11,09 (v/v) dan lama pemasakan selama 67,84 menit dengan nilai indeks tarik 44,1129 Nm/g dan indeks sobek 17,6678 mNm2/g. 5) Karakteristik fisik dan kimia pulp serabut sawit antara lain rendemen 41,95%, gramatur 125,33 g/m2, ketebalan 0,213 mm dan kadar air 7,26%.

11. SARAN 1) Pencarian hubungan antara NaOH dan HCl dalam proses delignifikasi lignin dalam serabut sawit. 2) Perlu dilakukan penelitian lebih lanjut tentang kandungan selulosa, lignin, dan hemiselulosa terhadap pulp dalam perlakuan terpilih.

DAFTAR PUSTAKA 1. Indriyati. 2008. Potensi Limbah Industri Kelapa Sawit di Indonesia. Pusat Teknologi Lingkungan Badan Pengkajian dan Penerapan Teknologi. Jakarta. Vol 4-no.1, hal 93-103 2. Tapanes, E., M.E. Nararjo, C. Aguero. 1992. Soda-Anthraquinone Pulping of Bagasse. Non Wood Plant Fiber Pulping Progress Report. TAPPI Press. Atlanta. 3. Saenah, E. 2002. Pengaruh Dosis Soda terhadap Karakteristik Pulp Abaca dan Pulp Kenaf Pulping Soda-Antaquinon. Skripsi. Jurusan Kimia. FMIPA. Universitas Brawijaya. Malang. 4. Sridach, W. 2010. Pulping and Paper Properties of Palmyra Palm Fruit Fiber. Department of Material Product Technology. Fakulty of Agro-Industry Prince of Songhkla University. Songkhla.

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5. Montgomery, D.C. 2001. Design and Analysis of Experiment 5th Edition. John willey and Sons, Inc. New York 6. Seth, R.S and P.H, Dage. 1988. Sifat-Sifat Serat dan Ketahanan Sobek. Tappi Journal. 71(2):52-58 7. Casey, J.P. 1981. Pulp and Paper, vol II 2nd edition. International Publisher Inc. New York. 8. Jahar, M.S., Lee, Z.Z., Jin, Y. 2006. Organic Acid Pulping of Rice Straw : Cooking. Pulp and Paper Research Division, BCSIR Laboratories. Dhaka. 9. Sidebang, E.B.R. 2008. Pembuatan dan Karakterisasi Kertas yang dibuat dari Kantong Semen Bekas dengan Pulp Batang Kelapa Sawit. TESIS. Jurusan Fisika Universitas Sumatera Utara. Medan. 10. Hadipernata, M., Budiyanto, A., Wiraatmadja, S., Sugiharto, A. 2000. Efisiensi Proses Pemutihan Pulp KRAFT RDH (Rapid Displacement Heating) dengan Metode ECF (Elementary Chlorine Free). Fakultas Teknologi Pertanian, Institut Pertanian Bogor. Bogor. 11. Pribadi, N.K. 2009. Optimasi Proses Penambahan Larutan NaOH dan Lama Pemasakan dalam Pembuatan Pulp dari Serat Batang Pisang. Jurusan Teknologi Industri Pertanian, Fakultas Teknologi Pertanian, Universitas Brawijaya. Malang.

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Khusus: Artikel Pemenang TICA 2011 (Cluster I)

Analysis of Damping Effectiveness as a Link between Shear Wall â&#x20AC;&#x201C; Shear Frame in Dual System Structure

| First Prize

Yoas Yuniananta1, Jessica Gunawan1 Department of Civil Engineering, Tarumanagara University

E-mail: yoas_y@yahoo.com, cika_cidin@ymail.com

Abstract Shear wall could be an alternative design to improve the durability of high-rise buildings against lateral forces including earthquake force. Shear wall is a rigid vertical diaphragm that is capable of resisting internal forces, e.g. normal forces, lateral forces and moment. However, internal forces, which are dominant in the shear wall, would influence the frame, especially the beam, and they would cause damage to the beam. In order to anticipate the damage, we could add a type of damper that could dissipate the seismic energy. The damper could be placed in the connection between two sub-systems of beams and shear walls. Both sub-systems are connected by means of springs and damper in parallel configuration. In this study, the damping effectiveness would be analyzed for 5-story regular building with 10 Degree of Freedom (DOF). The 5-story regular building was modeled in multi degree of freedom (MDOF) with mass-spring-damper system. Simulations in this study were done by iteration method of using MATLAB program. Newmark method was used to solve the structural dynamics equation. The results showed that the effectiveness of damper is not proportional to the ratio of natural period of the structure, Tn, of the seismic forces period, Tg, (Tn/Tg). The effective value of damper is 4,000,000 Ns/m with minimum percentage of base shear force of 66.0198%. It occured during Tn/Tg = 2.5. keywords: Damper, damping, earthquake force, structure dynamics, shear wall. ÂŠ2011. Persatuan Pelajar Indonesia Jepang. All rights reserved.

1. Introduction Earthquake has always been an important topic in the design and structural strength. In the design of structure, exact calculation of gravity and lateral forces is very important. In high-rise building, lateral force is more dominant in causing structural damage, particularly lateral force due to earthquake. High lateral force

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occured on the weak structures could lead to a failure or considerable damage to the building. Shear wall could be an alternative design to anticipate this problem. Shear wall is a rigid vertical diaphragm that is capable to resist internal forces of the structure, such as normal forces, lateral forces and moment. The forces would be transferred to the beam that binds the shear wall1. The beam would receive a large force and experience damage. The amount of force resisted by shear walls would be strongly influenced by the magnitude of lateral force. An alternative lateral force control technique in structural design, especially during earthquake, is to add a system on a structure that could absorb most of the seismic energy, which is entering the building. This technique is called passive control system. This technique has two major functions. The first function is to shift the natural frequency by modifying the mass and stiffness of the structure. The second function is to damp the vibration by providing additional damper to the structure2. Additional damper is expected to increase energy dissipation capacity of a structure. The objective of this damper is to absorb a significant amount of seismic input energy, thus reducing the demand on the structural system. The damper may also increase the stiffness and strength of the structure in which they are attached3. Damper is also used as a link between shear wall and shear frame in dual system structure. This research aims to study the effectiveness of damping value in order to properly design the damper. The objective of this study is to examine the effectiveness of damping by determining the optimal value of damping in structures that could save costs in the construction process. In order to give a better focus of the problem in accordance with the purpose of research, the problem is limited as follows: • The structure of building consists of two sub-systems (portal and shear wall) • The lateral force is applied to the direction of the axis of structure • The analysis incorporates dynamic loads due to the earthquake • The analysis assumes multi degree of freedom system • The structure is a linear elastic model • The calculation is done using MATLAB program

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2. Method and Experimental Procedure This research analyzed 5-story building consisting of two sub-systems. There are frame structure and shear wall, which were modeled as 10 DOF (Figure 1). Each column and shear wall element consists of two DOF (Figure 2). The columns and shear walls are prismatic, and therefore, axial deformation is neglected. The size of the column used is 0.8 m x 0.8 m as many as 42 points. Columns were distributed evenly where the span is of 6 m. The building is one of the regular buildings with dimension of 54 m x 24 m. Both sub-systems were connected by spring and damper. The spring and damping were connected in parallel. The structure was modeled using mass-spring-damper system on a Multi Degree of Freedom (MDOF). The solution of structural dynamics equations was done by Newmark method4.

Figure 1. Model of a 5-story building (10 DOF)

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DOF 2

DOF 1 Figure 2. Degree of freedom for column element

Stiffness matrix of prismatic elements as depicted in Figure 2 is expressed by following equation I  12 E  3  h  2 E I  1 −  h3

E I 1 2 E I   1212EI −- 12EI   33 hh33   hh   1 2 E I 1 212EI E I   - 12EI   − 33 hh3 3   hh

(1)

1 2 E I  −  h3   1 2 E I   

where E is elasticity of column material, I is moment inertia of column and h is column height5. The input for data structure consists of (1) mass of the vibrated object, M; (2) stiffness of the spring, k; (3) damping of the system, Ci and (4) dynamic force. This simulation was done by iterative method using MATLAB program. The mass of the structure was assumed to be a lump mass on each floor. In this study, the lump mass consists of the mass acting on the portal and the mass acting on the shear wall. The combined mass of two sub-systems is used as the total mass (M), and it is shown by the following equation M= MDL + 0.3MLL

(2)

where subscripts of DL and LL are dead load and live load, respectively. Total stiffness of the structure is a combination of portal stiffness, shear wall stiffness and stiffness of the spring. Damping value that is used in the dual structure is an assumed value, while the additional damping values (Ci) were varied. In order to study the structural response of the periodic excitation, the structure is loaded by dynamic force. The dynamic force is applied in the form of a sinusoidal force as shown by the following equation

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P(t)=Mṻg (3) ṻg=ṻg0 sinϖt = ṻg0 sin 2π t (4) Tg where P(t) is sinusoidal force, M is lump mass on each floor, ṻg is earthquake acceleration (in gravitational acceleration, g, unit), ṻg0 is amplitude of acceleration (0.3g) and Tg is earthquake force period. Natural period of the structure was determined based on the relationship between mass and stiffness of the structure. The limit is 0.15n, whereby n is the number of floors6. The variables involved in this study include: • Independent variable • Dependent variable • Variable control

: earthquake force period ( Tg ), damping value (Ci)

: natural period of the structure ( Tn ) : percentage of base shear force

Analyses were done with a variation of damping values between 0 Ns/m < Ci < 10,000,000 Ns/m. The variation ratio between structural natural period and earthquake force period (Tn/ Tg) is given as follows: 7.5; 2.5; 1.5; 1.0714; 1.00; 0.9375; 0.8333; 0.6818; 0.5769; 0.5; 0.4412 and 0.3947.

3. Results and Discussion The analysis results of the percentage of the base shear force could be seen in Figure 3. The percentage of the base shear force is the ratio between the base shear forces with damping to the base shear forces without damping. In Figure 3, it is shown that if the damping value is added periodically to the building structure, the percentage of the base shear force would not continuously decrease. Instead, it would reach an optimum point, and thereafter, it would increase again. The relationship between the percentage of base shear force and Tn/ Tg on any additional damping values could be seen in Figure 4. Figure 4 shows that the most effective damping value is reached on the minimum percentage of the base shear force, which is at Tn/ Tg = 2.5 whereby the damping value is 4,000,000 Ns/m. However, if the damping value is increased, the percentage of the base shear force also started to increase again.

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Moreover, each value of Tn/ Tg has different effective damping value with its minimum percentage of base shear force as shown in Table 1. Based on Table 1, it could be seen that at resonance (Tn/ Tg = 1), the most effective damping is 1,500,000 Ns/m and the base shear force percentage is 89.0578%. However, this condition is not effective enough as compared to the time of Tn/ Tg = 2.5 when the percentage of base shear force is 66.0198%. In addition, it could be mentioned that the damping is not very effective when the earthquake force period is larger than the natural period of the structure (Tn/ Tg < 1).

If the value of Tn/ Tg> 1, the percentage of the base shear force could be decreased.

However, at a certain point, the percentage of base shear force is increased again. These results indicate that the effectiveness of the damping is not proportional to the ratio of Tn/Tg. There is a turning point where the damping is no longer effective and it even adds to the percentage of the base shear force. Thus, the damping should be planned and designed so that the addition of damping could function effectively.

Figure 3. Percentage of base shear force to damping value (Ci) for each Tn/ Tg

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Figure 4. The relationship between percentage of base shear force and

Tn/ Tg for each damping

value, Ci (unit of Ci is Ns/m)

Table 1. Optimal damping value with its minimum percentage of base shear force

Tn/Tg

Min. percentage

Ci (Ns/m)

of base shear force (%)

7.5

80.2237

2,000,000

2.5

66.0198

4,000,000

1.5

85.3480

2,000,000

1.0714

96.6782

500,000

89.0578

1,500,000

0.9375

79.7832

5,000,000

0.8333

89.5462

4,000,000

0.6818

93.3370

3,000,000

0.5769

96.3276

1,700,000

0.5

97.1322

1,700,000

0.4412

97.8567

1,700,000

0.3947

97.5204

3,000,000

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4. Conclusions Based on the analysis in this study, it can be concluded that if the given damping value in the building structure is high, the damping force is increased, while the force resisted by the spring would be reduced. Moreover, the greater the given damping value in the building would provide an optimal damping value in resisting the base shear force. However, after reaching an optimal value, additional damping value becomes ineffective. It is characterized by the increase of percentage of the base shear force. Additional damping would be ineffective, especially when Tn/ Tg < 1. In general, the effective value of damping in the building structure is different for each value of the ratio Tn/ Tg. However, based on this research, the damping effective value is 4,000,000 Ns/m with a minimum percentage of the base shear force of 66.0198%, which occurred during Tn/ Tg = 2.5.

Reference 1. Paulay T, Priestley M.J.N. Seismic Design of Reinforced Concrete and Masonry Buildings. USA: John Wiley & Sons, Inc. 1992: 500-501. 2. Paz Mario. Dinamika Struktur: Teori dan Perhitungan, 2nd Ed. Jakarta: Erlangga. 1987. 3. Ghali A, Neville A.M. Structural Analysis: A Unified Classical and Matrix Approach. London: Chapman and Hall Ltd.1978: 400-409. 4. Symans Michael D, Constantinou Michael C. Semi-active Control Systems for Seismic Protection of Structures: A State-of-the-Art Review. Engineering Structures. 1999, Vol. 21: 469-487. 5. Chopra Anil K. Dynamic of Structures: Theory and Applications to Earthquake Engineering. New Jersey: Prentice Hall. 1995: 164-165, 570. 6. Departemen Permukiman dan Prasarana Wilayah. Standar Perencanaan Ketahanan Gempa untuk Struktur Bangunan Gedung, SNI 03-1726-2002. Jakarta. 2002: 26.

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Impact of Destination Images and Evaluative Factors Toward Tourists’ Behavioral Intention of the Destination. Case Study: Old Batavia (Kota Tua) Taman Fatahillah Jakarta

| Second Prize

Anna M.Pratiwi and Hapsari Setyowardhani Department of Management, University of Indonesia E-mail: anna.m.pratiwi@gmail.com, hapsarisetyowardhani@yahoo.com

Abstract This research discusses the effect of a destination image and its evaluative factors (perceived trip quality, perceived value, and satisfaction) toward visitors’ behavioral intention, whether they will revisit and recommend the destination to the other people. We firstly use an exploratory research to get insight and understanding about research problem. Then, the result from the exploratory research will be used as an input for the conclusive (descriptive) research. A structural equation modeling with LISREL 8.5.1 program is used to process the quantitative data. The results of this research show that the most influential factor toward visitors’ behavioral intention is satisfaction. Furthermore, the following path appears as a result of testing the structural model: destination image, perceived trip quality, perceived value, satisfaction and finally behavioral intention.

1. Introduction Indonesia is a country of thousands of islands blessed with richness in potential tourism objects. To maximize these potentials and gain national income, government made a program ‘Visit Indonesia’ every year. Focusing in tourism development is not only concerned by Central Government, but also by provincial government such as Jakarta, the capital of Indonesia, with a tourism program called ‘Enjoy Jakarta’.

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Jakarta has 477 years of national history since the Padjajaran Kingdom era, followed by colonialism era of Portuguese, England, Netherland and Japan, independence proclamation of Indonesia and modern developing era. Jakarta has now turned into a megapolitan city, but its long history still can be traced in forms of old architecture buildings, landmarks and museums in several places. A special place where we can nicely learn Jakartaâ&#x20AC;&#x2122;s history and go back to the old era is Old Batavia (Kota Tua Jakarta). Old Batavia is just one of many destinations in the Enjoy Jakarta program issued by Provincial Government of DKI Jakarta. Governor Regulation Province DKI Jakarta Number 127 Year 2007 stated that Old Batavia as a historical, cultural and business area/region has to be maintained and reserved, because of its richness in artistic architectures and cultures, economics values, and it has a lot of potentials to be explored. Old Batavia is planned not only to be a tourism destination and conservation area, but also to be a central of creative industries. The creative industries to be explored, such as photography and cinematography, will be centralized in Fatahillah Park (Taman Fatahillah). Exploration of Old Batavia as a destination, conservation area and central of creative industries is in accordance with the revitalization concept of Old Batavia generated by Provincial Government of DKI Jakarta. Revitalization of Old Batavia is aimed to maintain and develop Old Batavia itself. Revitalization is diligently made with vision-missions and a master plan of Old Batavia. The master plan of Old Batavia itself has been created in 2008 and now is ongoing to be officially authorized by Governor of Jakarta. As per interview with Mr. Gozali1 (Head of Maintenance, Development, and Publication of Old Batavia Managerial), with progression on the revitalization by the time, image and opinion of people and tourists about Old Batavia will be much better. Moreover, touristsâ&#x20AC;&#x2122; appreciation to museums is increasing. It can be seen on the museum visiting rate which is higher from year to year. Old Batavia has been concerned not only by Provincial Government of DKI Jakarta, but also by Central Government which decided Old Batavia to be one of fifteen (Destination Management Organization) DMO. Similar to a product name or brand, tourist destination such like Old Batavia also has its own image. An image is a concept formed through the consumerâ&#x20AC;&#x2122;s rational and emotional interpretation, the two of which are closely intertwined2. Cognitive evaluations refer to the perceptions, beliefs and knowledge individuals have of an object. In this case, such

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evaluations have something to do with the cognitive or perceptive component of the tourism destination image, an image created on the basis of a set of attributes which would correspond to the resources, attractions or general tourism offer at the destination3. Destination image will affect satisfaction and tourist’s future behavior. In an early research, Ching-Fu Chen and DungChun Tsai4 investigated the effect between the following variables: effect of destination image on perceived trip quality, perceived value, satisfaction and tourist’s behavioral intention; effect of perceived trip quality on perceived value, satisfaction and tourist’s behavioral intention; effect of perceived value on satisfaction and tourist’s behavioral intention; and effect of satisfaction on tourist’s behavioral intention. By understanding the relationship between tourist’s future behavioral intention and its determinants (perceived trip quality, perceived value and satisfaction), destination tourism manager would better know how to build up an attractive image and improve their marketing efforts to maximize their use of resources4. With such an understanding, we decided Old Batavia as a research object, by investigating the effect of destination image of Old Batavia and its evaluative factors (perceived trip quality, perceived value and satisfaction) on tourist’s behavioral intention. This research then applies a research model described below3.

2. Methods 2.1. Theoretical Background and Hypotheses This study is proposed the hypotheses conducted by Ching-Fu Chen and DungChun Tsai4, as follows: H1. The more favorable the destination image, the higher the perceived trip quality. H2. The more favorable the destination image, the higher the satisfaction. H3. The more favorable the destination image, the higher the perceived value. H4. The more favorable the destination image, the more positive the behavioral intention. H5. The higher the perceived trip quality, the higher the satisfaction. H6. The higher the perceived trip quality, the more positive the behavioral intention. H7. The higher the perceived trip quality, the higher the perceived value.

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H8. The higher the perceived value, the higher the satisfaction. H9. The higher the perceived value, the more positive the behavioral intention. H10. The higher the satisfaction, the more positive the behavioral intention. Petrick5 classified the relationship quality, perceived value and satisfaction into three models, i.e. the satisfaction model (quality – value - satisfaction), the value model (quality – satisfaction - value) and the quality model (the relationship between satisfaction and value is uncertain). The empirical result shows in favor of the satisfaction model. Other words, perceived value plays a moderating role between quality and satisfaction. The proposed conceptual model of the study is shown in Figure 1. Each of the model can be defined as4: Destination image is the tourist’s subjective perception of the destination reality. Perceived trip quality is the tourist’s assessment of the standard of the service delivery process in association with the trip experience. Perceived value is the tourist’s overall appraisal of the net worth of the trip based on the tourist’s assessment of what is received (benefits) and what is given (costs or sacrifice). Satisfaction is the result from the ability of the trip experience to fulfill the tourist’s desires, expectations and needs in relation to the trip. Behavioral intention is the tourist’s judgement about the likeliness to revisit the same destination or the willingness to recommend the destination to the others.

Figure 1. Proposed Conceptual Model

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2.2. Exploratory and Descriptive Research Firstly, exploratory research was designed to gain understanding and insight about Old Batavia by having in-depth interview with Head of Publication of Old Batavia’s managerial and also by collecting secondary data from literature such as research articles and journals, internet publication and mass media. After gaining an in depth understanding about the issue, the descriptive research was carried out by designing the questionnaire as the survey instrument. The questions in the questionnaire are based on a review of the literature about early researches and based on the study of Old Batavia’s issues. Part 1 of questionnaire is about the destination image. Part 2 is the perceived trip quality. Part 3 is about the perceived value. Part 4 is about the satisfaction of a tourist. Part 5 is about the intention of a tourist after visitation. These are using six-point Likert type-scale, range from ‘strongly disagree’ to ‘strongly agree’. And the last, part 6 presents the respondent profile.

2.3 Sample Design and Data Collection The questionnaires were conducted during April to May 2010. Using convenience sampling, individuals over the age of 15 years (have been completed Junior High School) and who were visiting the Old Batavia (during a year at last) were considered to be the target population of this research. 220 questionnaires were spread out, and 210 were collected as usable samples. Total sample 210 was obtained by multiplying the sum of indicators in this research (total 42 indicators) with 5, in order to get the number of adequacy samples to be proceed with LISREL6. The respondent profile is summarized in Table 1.

2.4. Data Analysis Pretesting of questionnaires was applied to 30 respondents as sample. Pretesting is important to identify whether the wording, layout and information in the questionnaire will be clear enough and understand by respondent. In addition, pretesting is applied due to minimize the potential problem that would be happened because of unpleasant data value7. Pretesting was proceeded with reliability and

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validity procedure. The evaluation and renewal of questionnaire was then made using the reliable variables, and the fixed questionnaires were then spread out again to respondents. Frequency distribution analysis was applied to reflect the information and characteristic of respondent. Structural Equation Modeling (SEM) was conducted to test the hyphotheses using LISREL 8.51. Table 1. The Summary of Respondent Profile

Respondent Profile

Frequency

(%)

Gender Male

38.1 %

Female

130

61.9%

192

91.4%

25-34

7.1%

35-44

1.4%

Primary/Junior high

2.4%

Senior high school

21.4%

28.1%

Age 16-24

Education level

Diploma Bachelor degree

100

47.6%

Postgraduate

0.5%

Student

17.1%

University student

128

61%

Employee of private sector

14.8%

Government employee

3.3%

Entrepreneur

1.4%

Other

2.4%

1-2 time(s)

150

71.4%

3-5 times

19.5%

6-8 times

4.3%

9 times or more

4.8%

Family and friends

169

80.5%

Tour guide/tour agent

2.4%

Articles and mass media

8.1%

Internet

5.7%

Others

3.3%

Occupation

Visitation frequency to Old Batavia per year

Source of information

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Source: Frequency distribution analysis using SPSS 17

3. Results and Discussion Reliability for each constructs and factors were obtained by calculating the Cronbach’s α coefficient. The Cronbach’s α coefficient over 0.60 means items/questions appeared in the questionnaire are reliable8 and can be proceeded further into SEM calculation. Factor ‘Tourist-cultural management’ and ‘Amenity’ were eliminated because of unreliable (the Cronbach’s α coefficient is below 0.60) and insignificant to the model. The result of Cronbach’s α testing is shown in Table 2. Table 2. Reliability Result

Construct

Cronbach’s Alpha

Destination Image Factor: Beauty of the historic–cultural heritage and feelings generated by its perception

0.7161

Clean and peaceful atmosphere, and feelings generated by its perception

0.7365

Maintenance/integration of site architecture Historic-scenic Wealth

0.6544

Complementary tourist offer or infrastructure

0.8201

Perceived Trip Quality Factor: Hospitality

0.6373

Attraction

0.6306

Accessibility

0.6292

Satisfaction

0.7402

Perceived Value

0.865

Behavioral Intention

0.8106

Source: Cronbach’s Alpha testing using SPSS 17

Confirmatory Factor Analysis (CFA) was then conducted using LISREL 8.51. CFA is

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applied to measure whether the observed variables can reflect its latent variable6. The summary of CFA is shown in Table 3. Table 3. CFA Result

Source: CFA testing using LISREL 8.51

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The proposed conceptual model in the Figure 1 was then measured using five constructs consist of ‘destination image’ (measured by five factors and 19 items in total), ‘perceived trip quality’ (measured by three factors and 10 items in total), and then ‘satisfaction’, ‘perceived value’ and ‘behavioral intention’ were measured by five, three and two items. The summary of structural model’s statistic testing is shown in Table 4. It can be seen that all of goodness of fit indices resulted ‘good fit’ and ‘perfect fit’. Table 4. Goodness of Fit – Structural Model

Source: Goodness of Fit testing using LISREL 8.51

In Figure 2, the estimated structural model was obtained for defining the proposed hypotheses. Destination image has significantly positive effect on perceived trip quality and satisfaction (γ1=0.3, t-value=4.51; γ3=1.24, t-value=3.80) hence supported H1 and H2. H3 and H4 are not supported because their coefficient are insignificant (destination image->perceived value γ2=-0.13, t-value=-0.39; destination value-

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>behavioral intention γ4=0.18, t-value=0.55). Perceived trip quality has significantly positive effect on perceived value (β1=2.69, t-value=2.74) supporting H7, but not supporting H5 and H6 because it doesn’t have significant effect on both satisfaction and behavioral intention (β2=-0.73, t-value=-0.80; β3=1.40, t-value=1.41). Perceived value has significantly positive effect on satisfaction (β4=0.42, t-value=3.48) supporting H8, nevertheless, doesn’t have significant effect on behavioral intention (β5=0.044, t-value=0.29) not supporting H9. Lastly, satisfaction has positive effect on behavioral intention (β6=0.48, t-value=4.51) supporting H10. Summary of hypotheses testing is indicated in Table 5.

Figure 2. The Estimated Structural Model

Table 5. Summarry of Hypotheses Testing Result

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To summarize, from the measurement of structural model the evident path is obtained by ‘destination image g perceived trip quality g perceived value g satisfaction g behavioural intention’. The direct and indirect effects of all constructs are shown in Table 6. Only satisfaction has direct effect on behavioral intention, while destination image, perceived trip quality and perceived value have indirect effect on behavioral intention. It indicates that satisfaction is the strongest variable to influence tourist’s behavioral intention. But, note that destination image, perceived trip quality and perceived value have indirect effect on tourist’s behavioral intention (through path destination image g perceived trip quality g perceived value gsatisfaction g behavioral intention). Table 6. Dirrect, Indirrect and Total Effect

Source: SEM using LISREL 8.51

Referensi 1. Gozali. (2010, Maret 31). Personal Interview. 2. Baloglu S, McCleary KW. A model of destination image formation. Annals of Tourism Research. 1999. 26(4): 868-897. 3. Stabler, MJ. The image of destinations regions: theoretical and empirical aspects. Marketing in tourism industry: The promotion of destination regions. London: Goodall & Ashworth. 1995: 133–159. 4. Chen Ching-Fu, Tsai DungChun. How destination image and evaluative factors affect behavioral intentions? Journal of Tourism Management. 2007. 28: 1115-

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1122. 5. Petrick JF. The roles of quality, perceived value and satisfaction in predicting cruise passengersâ&#x20AC;&#x2122; behavioral intentions. Journal of Travel Research. 2004. 42(4): 397407. 6. Hair, Black, Babin, Anderson, Tatham. Multivariate Data Analysis, 6th ed. New York: Prentice Hall. 2006. 7. Sekaran, Uma. Research Methods for Business: A Skill Building Approach, 4th ed. New Jersey: John Wiley & Sons Inc..2003. 8. Malhotra Naresh K. Marketing Research: An Applied Orientation, 5th ed. New York: Prentice Hall. 2007.

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Hidden Pattern Average : A New Technical Indicator for Securities Price Pattern Prediction

| Third Prize

Fietra Riva Harvadi University of Indonesia E-mail : riva.harvadi@yahoo.com

ABSTRACT There are two types of analysis that can be used in analyzing stock prices, namely fundamental analysis and technical analysis. Technical indicator is one of many forms of technical analysis, which is quite popular due to its easy interpretation. Its use is also quite practical because it is supported by information technology advances. However, technical indicators that currently exist canâ&#x20AC;&#x2122;t provide a clear picture of stock prices movement in the future. Hidden pattern average is a new technical indicator that created by author, in which able to outperform this weakness. These technical indicators are able to read hidden patterns of security prices movement by analyzing its historical prices through eight steps. This technical indicator also enables its users to maximize investing profit and manage the price fluctuation risks. This technical indicator is application of the chain of events method1 in the financial subject, where the chain of events method is a method that made by author that can be used to predict the pattern of nominal and ordinal data types. The author has tested this indicator by predicting 80 adjusted close price data of DJIA and NIKKEI 225 indexes and compare it with actual data. Based on the result, the author concluded that this indicator is able to predict the prices pattern very well. However, like other technical indicators, it has some limitations because its accuracy is vulnerable to unexpected events in the future. keywords : New Technical Indicator, Stock Price Movement Analysis Tools, Stock Price Pattern Prediction, Investment Profit Maximization and Risk Management.

1. INTRODUCTION Before making a decision to invest in the stock market, it is important to perform analysis on the company which shares will be worth to invest in, the acceptable price per share and timing to buy or sell shares. There are two types of analysis that can be used, namely fundamental analysis and technical analysis. Fundamental analysis

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is the stocks value and prospect analysis based on its natural factors, like inflation, net income, etc. Meanwhile, technical analysis is based on the patterns of past stock prices movement. Typically, investors use fundamental analysis to determine which stocks are prospective and technical analysis to determine when and at what price should investors buy or sell shares. Technical analysis can be done by using technical indicators. Technical indicator is a statistical formula that designed to be an indicator of certain behavior of stock prices. All technical indicators are basically useful to predict, but they cannot always provide a clear picture of the stock price movement in the future. Such weakness may lead investors to disadvantageous investment decisions. In this context, the author introduces the hidden pattern average as a new technical indicator which is expected to outperform this weakness. Hidden pattern averages give us a clear picture of the securities prices pattern prediction in a spesific span of time in the future. This technical indicator is able to read hidden patterns of a security by analyzing its historical prices through several steps. After the hidden pattern is legible, it is possible to predict the stocks prices movement pattern in the future. This method is the application of the chain of events method1 in the finance subject.

2. METHOD AND EXPERIMENT PROCEDURE To test the hidden pattern average indicator, the author make eight pattern predictions of the NIKKEI 225 and DJIA indexes using the hidden pattern average and compare it with actual data patterns. Each prediction consists of ten predicted data of the future. All historical data are collected from yahoo finance.

2.1 Hidden Pattern Average Analysis Steps This technical indicator consists of eight steps of analysis. The first step is determining the amount of historical data. The author uses 115 daily stock prices as historical data to predict ten days forward for each pattern prediction. It should be noted that using too few historical data will make the prediction results more susceptible to the future fluctuations. However, too much historical data to calculate means including obsolete data that may no longer be relevant to current conditions. The second step is converting quantitative data into qualitative data. Before doing the conversion, we must first determine what kind of stock price that we want to predict, whether it is opening prices, closing prices, high, low or the other prices. In this paper, the author decided to predict the adjusted close prices. After that, the

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historical data is sorted up in order of time and then the stock price percentage changes relative to previous data(t-1) are calculated. This can be notated as [ ( ( Data(T) ) - ( Data(T-1) ) ) / ( Data(T-1) )] * 100%. The positive percentage then labeled as “I” which means increasing, and labeled as “D” for a negative percentage which means decreasing. Table 1. Illustration of step two

Adjusted Close

Percentage of

Event Label

Increase 0 1 2 3 4 5

10279,19 10355,99 10292,63 10344,54 10228,92 10398,1

0,747140582 -0,611819826 0,504341456 -1,117691072 1,65393805

I D I D I

The third step is fractalization. In this step, the data is divided into several groups after considering the amount of data. The data group will be increased by one group for every five increase in data prediction. In this experiment the author divides the historical data into two groups, namely fractal 1 and fractal 2, because the author would predict ten data forward. The data grouping is based on the data time code. Data t, t+2, t+4, and so on will be grouped as fractal 1, while data t+1, t+3, t+5, and so on will be grouped as fractal 2. Table 2. Illustration of step three

Fractal 1 T 1 3 5

Adjusted Close

Percentage of

Event Label

10355,99 10344,54 10398,1

Increase 0,747140582 0,504341456 1,65393805

I I I

Adjusted Close

Percentage of

Event Label

10292,63 10228,92

Increase -0,61181983 -1,11769107

D D

Fractal 2 t 2 4

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The fourth step is vertical analysis. This analysis is performed by determining all possible combinations of three labels and then record the frequency of occurrence of these combinations, like this following example: Table 3. Illustration of vertical analysis

The Possible Events Combination D --> D --> D D --> D --> I D --> I --> I D --> I --> D I --> I --> I I --> I --> D I --> D --> D I --> D --> I

Frequency 0 0 0 0 2 1 0 1

Probability 0 0 0 0 0,5 0,25 0 0,25

In practice, the users of this indicator can increasing the number of labels for each combination to improve the pattern reading accuracy. However, in this paper, the author used three labels for each combination. Noted that vertical analysis is performed per fractal. The fifth step is horizontal analysis. In this analysis, the frequency of the events combination that occurred successively are recorded. This analysis is used to determine when is the same events that occur in a row will be end. The sixth step is the proportion analysis. In this analysis, the author calculate the expected frequency of each event ( I & D ) by calculating the probability of occurrence of each event and then multiplied it by the number of prediction that you want done. The analysis is performed per fractal from step three until step eight. The seventh step is making prediction. Prediction is done by taking into account the results of vertical, horizontal and proportion analysis. As an example, it was assumed that there were 10 events to predict in the future by using 20 historical data. If the results of vertical analysis of fractal 1 is I  D  I = 70%, D  I  D = 80%, the proportion analysis of fractal 1 is “I” = 3, “D” = 2, and the 17th and the 19th data label are “I” and “D”, then the predictions for fractal 1 are as follows:

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Table 4. Illustration of step seven

T Event

17 19 I D Historical

21 I

23 D

25 27 I D Periodiction

29 I

The eighth step is converting qualitative data into quantitative data. The prediction from step seven is still in the form of qualitative data, namely “I” and “D”. We should convert this label into stock price, in the form of currency. To do this, we should convert these labels into the form of a percentage of change first. Determination of the percentage of change in stock price for each label is different for each events combination. For example, the percentage of change in stock price for the combination I  I  D and D  D  I will be different even though they both produce the event “I” at the end. Determination of the percentage of change in stock price is based on the average percentage of change from the historical data for each events combination. After the average percentage of change in the stock price is determined for each label, the next thing is converting the average percentage of change into stock price by multiplying the average percentage of change (for label “I”, the average percentage of change is added by 1 first before multiplication. For label “D “, the average percentage of change is substracted by 1 first before multiplication.) with the actual stock prices, exactly before prediction started, like this following example: Table 5. Illustration of step eight.

115 116 117 118 119 120 121 122 123 124 125

Fractal

2 1 2 1 2 1 2 1 2 1

Event Prediction

D I I D D I I D I I

Combination

D-->I-->D I-->D-->I I-->D-->I D-->I-->D D-->I-->D I-->D-->I I-->D-->I D-->I-->D D-->I-->I I-->D-->I

Average Percentage of Change -0,0081754 0,00802834 0,00691193 -0,0071364 -0,0081754 0,00802834 0,00691193 -0,0071364 0,00754451 0,00802834

Prediction

9411* 9334 9409 9474 9406 9329 9404 9469 9402 9473 9549

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The data at t = 115 in column â&#x20AC;&#x153;predictionâ&#x20AC;? (9411) is actual data. Actual data is then multiplied by the percentage of change to produce predictions for the t = 116 data. Then, the t = 116 prediction data will be a basis for predicting the t = 117 data and so on. After knowing all of the stock price predictions, then we plot this predictions into a graphical form to facilitate the interpretation of the pattern prediction.

3. RESULTS AND DISCUSSION Here is the hidden pattern test results that conducted by the author. The author made eight pattern predictions of the NIKKEI 225 and DJIA indexes using the hidden pattern average and compare it with actual data patterns. Each prediction consists of ten predicted data of the future. All historical data are collected from yahoo finance.

Graph 1. The comparison of the pattern prediction and the actual data from the NIKKEI 225, dated as 16/06/2011 to 30/06/2011

Graph 2. The comparison of the pattern prediction and the actual data from the NIKKEI 225, dated as 29/07/2011 to 12/08/2011

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Graph 3. The comparison of the pattern prediction and the actual data from the NIKKEI 225, dated as 30/06/2011 to 14/07/2011

Graph 4. The comparison of the pattern prediction and the actual data from the NIKKEI 225, dated as 14/07/2011 to 29/07/2011

Graph 5. The comparison of the pattern prediction and the actual data from the DJIA, dated as 14/06/2011 to 28/06/2011

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Graph 6. The comparison of the pattern prediction and the actual data from the DJIA, dated as 14/07/2011 to 28/07/2011

Graph 7. The comparison of the pattern prediction and the actual data from the DJIA, dated as 29/06/2011 to 14/07/2011

Graph 8. The comparison of the pattern prediction and the actual data from the DJIA, dated as 28/07/2011 to 11/08/2011

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From these test results, the author found that hidden pattern average is able to predict the securities pricesâ&#x20AC;&#x2122;s actual pattern as well. Different from the existing technical indicators, analysis using this indicator is able to provide a clear picture of the stock prices movement in the future. However, some test results were not able to predict the pattern very well. Not only founded in the hidden pattern average, such weaknesses are common in other types of technical analysis which are based merely on historical data. It does not consider macroeconomic factors, natural disasters or other factors that also affect the actual price movements of securities. Therefore, the accuracy is vulnerable to unexpected events in the future.

4. CONCLUSION It has been proven that hidden pattern average is able to read and predict the stock price pattern well and able to give a clear picture of the stock prices movement in the future, unlike the other technical indicators. However, this indicator still has the weaknesses similar to other technical indicators, in which the accuracy of prediction is vulnerable to unexpected events.

5. REFERENCE 1. Jones, C. P. et al. Investments : Analysis and Management. Brian Kamins (Ed.). New Jersey : John Wiley. 2007. 2. Wira, D. Analisis Teknikal Untuk Profit Maksimal. Jakarta : Exceed. 2011. 3. URL : http://finance.yahoo.com/q/hp?s=^N225+Historical+Prices 8 September 2011. 4. URL : http://finance.yahoo.com/q/hp?s=^DJI+Historical+Prices 8 September 2011.

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PERFORMANCE EVALUATION OF SHEAR WALL SYSTEM IN REINFORCED CONCRETE TALL BUILDING

| Finalis 1

Vicktor Hugo Juanda1 1

Department of Civil Engineering, Tarumanagara University

E-mail : vicktor_hugo@ymail.com

ABSTRACT This paper provides the performance evaluation of shear wall system in reinforced concrete tall building. Tenth-story symmetrical buildings with three different cases are designed in accordance with the latest Indonesian Seismic Code (SNI 03-17262002). At the first case, buildings use intermediate moment resisting frame. Second case, buildings use structural wall system with variation of shear wall location. The third case, buildings use structural wall system with variation of the number of shear wall. Ductility and seismic reduction factor would be compared for all variations of buildings. The performances of the observed structures are determined by nonlinear static pushover analysis using ETABS v9.2.0. The results show that ductility of structure with shear wall is larger than structure with intermediate moment resisting frame. However, the larger number of shear wall not always makes the structure more ductile. Based on the results, it is concluded that seismic reduction factor in Indonesian Seismic Code still safe to be used, while pushover analysis could provide the exact information about seismic reduction factor. Thus, we could have economical structure design and reliable. keywords: Ductility, pushover analysis, seismic reduction factor, shear wall, structural wall system.

1. INTRODUCTION Indonesia is one of the vulnerable area to earthquake, both tectonic and volcanic earthquake. This is because, Indonesia is located in three large plate of the earthâ&#x20AC;&#x2122;s crust such as the Indian Ocean, Australia, Pacific, and Continental Euro Asia and micro-Philippine plate that could collide and interact with each other. Earthquake can cause damage to various elements of tall buildings; even strong earthquake could cause the collapse of the building.

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Most of the earthquake victim was buried by collapsed buildings that do not withstand the shocks of earthquakes. So a structural engineer must know about dynamics of structures in order to resist the earthquake forces and how buildings respond to ground acceleration caused by the earthquake in accordance with Newtonâ&#x20AC;&#x2122;s second Law of motion. Nowadays, the development of the structural system is very advanced, so the building can reach more than 100 stories. However, when the structure was designed based on the maximum 500-year returned period of earthquake and structural response is elastic, that the cost of the structure should be high and not economical. In order to reduce the cost of such structures, ductility has a significant role that expected to be inelastic structural response during the earthquake load and considered the safety of human life (minimum casualty). Performance of serviceability limit of the structure is determined by the story drift. The purpose is to preventing non-structural damage. Moreover, it could limit the occurrence of yield strength of steel and excessive crack in concrete. At this time, three methods of performance-based design are known, i.e. capacity spectrum method (ATC-40, 1996), N2 method (Fajfar, 2000) and direct-displacement design method (Priestley, 2000). Pushover analysis is performed by Displacement coefficient method/Capacity spectrum method. It is based on performance analysis. Pushover analysis is a static, nonlinear analysis in which the magnitude of the seismic and structural loading is incrementally increased in accordance with a certain predefined pattern. With the increase in the magnitude of the loading, the first plastic hinge and failure modes of the structure would be found. 1, 2 The structure model used in this paper will be evaluated using the seismic behavior of pushover analysis method according to ATC- 40.

1.1 The Purpose and the Goal The purpose of this study was to determine and evaluate the performance of reinforced concrete buildings with shear walls system, especially regarding the ductility and resistance to earthquakes. While the goals are: 1) To study the characteristics of a reinforced concrete building structures with shear

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wall frame system with in terms of ductility; 2) To compare the ductility of reinforced concrete building using a structural wall system with variations in shear wall location; 3) To compare the ductility of reinforced concrete building using a structural wall system by adding variations of the shear wall number.

1.2 The Limitation of Problem Modeling analysis of the structure using ETABS program V.9.2.0.3 The limitation of problem in this study are as follows: a) The structure model are tenth-story symmetrical buildings that designed in accordance with Indonesian Seismic Code (SNI 03-1726-2002) and Concrete Building Code (SNI 03-2847-2002); b) Dead load and live load used for office building in accordance with Indonesian Loading Code for Building (PPIUG-1983); c) The entire building use compressive strength of concrete fâ&#x20AC;&#x2122;c = 24.9 MPa with longitudinal and transverse reinforcement are using ultimate tensile strength fy = 400 Mpa; d) Losses and creep that could occur in the structure of the material components are not considered; e) The joints between components of structure are fully rigid.

2. METHOD AND EXPERIMENT PROCEDURE The moment capacity of columns is designed larger than the capacity of beams in order to (put verb e.g. make/facilitate) plastic hinge is occurred in beams not in columns, except bottom colum and on top of supporting roof column. These could happen with the concept of strong column weak beam. Failure modes of the structure that expected is beam side swaying mechanism, and soft story mechanism is avoided (Figure 2a). 4

(a)

(b)

Figure 1. (a) Beam side sway mechanism. (b)Soft story mechanism

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Ductility of structure is strongly influenced by inelastic behavior of structures due to the formation of plastic hinges on the structural elements. Ductility values associated with a seismic reduction factor that usually specified by building codes. SNI 03-17262002 adopt seismic reduction factor of UBC 1997. This seismic reduction factor could be determined by pushover analysis. Thus, we could compare its value between the code and the results of analysis. Ductility factor of structure (µ) could be defined as the following equation:

D u Dy

(1)

where u is maximum lateral displacement at the end of plastic deformation, and y is lateral deflection when the first yielding is reach. Moreover, according to experiments of dynamic analysis, relationship between elastic-elastoplastic systems could be defined as the following equation:

1 m

(2)

where R is force reduction factor. 5 In this study, column elements are using default-PMM as type of hinge properties in ETABS, with the consideration that there is an interaction between axial force and moment (P-M interaction diagram). The beam elements using moment hinge properties (Default-M3), with the consideration that beams are effective in resisting moment at the strong axis (axis-3). Thus, expected the plastic hinge would occur in the beam. Plastic hinge would be determined by ETABS automatically. Structural elements that allowed having plastic hinges are: 1) Beams The plastic hinges caused by moment on its flexure direction, so plastic hinges defined as a default-M3-0 and default-M3-1 2) Columns The formation of plastic hinges at the end of columns was caused by interaction between flexure and compress direction in two way axis of seismic loading. Hinge properties that used is default-PMM-0 and default-PMM-1. In general, the procedures of pushover analysis in this paper are as follows: 1) Magnitude of the lateral loading is incrementally increased that distributed along the height of structure design; 2) Check the lateral deflection on roof floor and diagram P-∆ from analysis output from ETABS v9.2.0 program; 3) Determine the maximum lateral deflection (Δ u) and lateral deflection when the

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first yielding is reach (Î&#x201D; y) to obtain the value of ductility factor with equation (1) and force reduction factor, R = Îź.f1 where f1 = 1.6; 4) Limitation of natural period of the structure, T1, based on SNI 03-1726-2002. The purpose of this limitation is to keep safe the flexibility of structure.

3. RESULTS AND DISCUSSION In this paper, a study performed in open frame structure with variations layout of the shear wall as shown in Figure 2.

Figure 2. Variations layout of the shear wall in ETABS v9.2.0

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Based on results of ETABS pushover analysis, the value of µ and R could be calculated according to equation (1) and (2). The value could be seen in Table 1 and Figure 3. Table 1. The results of structure analysis

x-direction

y-direction

∆max

∆y

∆max

∆y

Frame system

0.456

0.114

6.43

0.444

0.0994

7.14

Structure 1

0.417

0.085

7.84

0.418

0.071

9.41

Structure 2

0.432

0.071

9.75

0.406

0.0568

11.4

Structure 3

0.440

0.071

9.93

0.406

0.0568

11.4

Structure 4

0.289

0.043

10.84

0.279

0.0426

10.5

Structure 5

0.390

0.071

8.79

0.375

0.0568

10.6

Figure 3. Seismic reduction factor curve

In this study, the natural period of structures, T1, are checked for each variation layout of shear wall as shown in table 2.

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Table 2. Natural period of structure, T1

Number of FLoors (n)

Allowable T1 = 0.18*n (second)

0.18

T1 (second) Open Frame Layout 1 Layout 2 Layout 3 Layout 4 Layout 5

1.4842 0.9634 0.9602 0.7785 0.6934 1.0759

Status OK OK OK OK OK OK

Based on Table 2, it could be seen that all types of structures investigated in this study fulfill the requirements of allowable natural period of the structure according to SNI 03-1726-2002.

4. CONCLUSION Based on the results of pushover analysis using ETABS v9.2.0, it is concluded : 1) Structural wall system is more ductile than open frame structure with intermediate resisting moment frame, because almost lateral forces resist by shear wall; 2) The first plastic hinge is more faster to performed at structural wall system than intermediate resisting moment frame; 3) Layout 3 as described in Figure 2 have more stiffness and ductility than other layouts. It is concluded that shear wall is more effective if it is distributed to form core wall. 4) Variation layouts of shear wall is influenced the ductility of structure. So, the larger number of shear wall is not always proportional with more ductile of structure. 5) Pushover analysis could find the pattern of plastic hinges that performed and the failure modes of structure, so structural engineer could avoid the performed of plastic hinge in columns; 6) Seismic reduction factor in SNI 03-1726-2002 still safe to be used, while pushover analysis could provide the exact information about seismic reduction factor.

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5. REFERENCE 1. Dewobroto W. Evaluasi Kinerja Struktur Baja Tahan Gempa dengan Analisa Pushover. Presentation and Proceeding at the Civil Engineering National Conference Sustainability Construction & Structural Engineering Based on Professionalism. Unika Soegijapranata, Semarang. 17-18 Juni 2005. 2. Adhikari S. Pushover Analysis. URL: http://www.sefindia.org/ forum/viewtopic. php?t=7662 accessed on Maret 30, 2011. 3. Department of Civil Engineering University of California Berkeley. ETABS Version 9.2.0: Integrated Building Design Software. USA. 2006. 4. Lumantarna B, Muljati. Performance of Partial Capacity Design on Fully Ductile Moment Resisting Frame in Highly Seismic Area in Indonesia. Presentation and Proceeding at Eleventh East Asia-Pacific Conference on Structural Engineering & Construction (EASEC-11). Taipei, Taiwan. Nov 19-21, 2008. 5. Soegiarso R, Sunarya H. The Strength of The Tall Structures Beyond The Elastic Region. Jurnal Teknik Sipil, Universitas Tarumanagara. 1999, Vol. 5(No.1): 1-10.

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The Role of Vocational High School in Improving National Competitiveness: Analysis and Recommendation

| Finalis 2

Budiono, Harizah Persiana Mangkunegara, Ayu Yeriesca Department of Economics, University of Indonesia E-mail : budiono.ie@gmail.com, harizahpersiana.m@gmail.com, ayeriesca02@gmail.com

Abstract Education plays an important role in enhancing competitiveness and economic growth. This paper aims to analyze the role of vocational education in enhancing the competitiveness of Indonesia. Vocational education provides the opportunity for people to acquire practical skills, either to enter the job market or to create employment through entrepreneurship. Furthermore, this paper will provide analysis of the significance of the solution in solving the problem empirically, based on a research using multiple regression analysis. The result of multiple regression analysis proves that the number of vocational high school (SMK) graduates is the most significant variable in describing variance in regional gross domestic product in Indonesia. This is also in line with previous research on a significant role of vocational education in improving competitiveness and economic growth. Based on discussion and empirical evidence, we can conclude that enhancing the role of vocational high school is the right solution to improve the national competitiveness and promote regional economic growth. keywords: human capital, education, competitiveness, regression analysis ÂŠ2011. Persatuan Pelajar Indonesia Jepang. All rights reserved.

1. Introduction Competitiveness has significantly affected economic performance of a country. Moreover, current international economy is increasingly integrated, both in global and regional scope. As an implication, competition between nations has become inevitable to deal with. The low competitiveness of a country will hamper economic growth in the country because of competition from other countries, which will inhibit the increase in the welfare state. Therefore, increasing competitiveness has become a crucial agenda for all countries in the world, especially developing

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countries, to achieve high economic growth, and then to improve the welfare and to reduce poverty. The competitiveness of a nation is influenced by several factors. Based on the determinants of competitiveness, there are three main areas that are used to explain economic growth, namely: education and training (human capital), the use of information and communication technology, and innovation and technological adaptation (Chen & Dahlman, 2004; Porter et al., 2004 in Sahlberg).1 Asian Development Bank (ADB) in â&#x20AC;&#x153;Country Diagnostics Studies, Indonesia: Critical Development Constraintsâ&#x20AC;? identifies major constraints that hinder development in Indonesia. 2 The main constraints include three aspects, namely: the infrastructure, institutional and education (human capital). First, inadequate and poor quality of infrastructure, particularly transport networks, power supplies and irrigation in some provinces. Second, weak governance and institutions, marked by numerous cases of corruption, less effective role of government, and several occurrences of terrorism and violence in some areas. Third, unequal access and poor quality of education, especially vocational education, failed to increase the quality of human capital. These obstacles decelerate economic growth and hamper the creation of opportunity and equity among regions. These constraints are also the cause of the weak competitiveness of Indonesia. From the explanation above, it can be concluded that the aspect of education (human capital) plays an important role in enhancing competitiveness and accelerating economic growth. The role of education is different depending on the stage of economic growth in the economy and the structure facing the country. According to Porter (in Kwiek, 2008), for countries experiencing growth, competitive advantages and modes of competing of a country slowly changes from factor-driven stage (characterized by low-cost labor, natural resources rich) to the investmentdriven stage (characterized by the presence of foreign technology, imitation), and then to the fullest, innovation-driven stage (characterized by innovative products and services).3 In the first stage, basic education plays the dominant role, whereas in the second stage, the dominant role is played by secondary education, and higher education has the dominant role in the third stage. Indonesiaâ&#x20AC;&#x2122;s economy is currently entering a period of transition to the second stage, investment-driven stage, so the secondary education has a significant role in determining the competitiveness of nations. Inevitably, the role of vocational high school (SMK) is also increasingly

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important in light of this second stage that requires the mastery of foreign technology and the ability of technology imitation. In addition to improve competitiveness, education is also able to empower the community because education helps a person become more proactive in economic, social and political activities. Education gives a person the opportunity to earn a decent living so that they can get out of poverty. Without education, people will tend to be marginalized in the broader social sphere (ADB, 2003).4 Therefore, education is one of important strategy in community empowerment. Based on the background, this paper tries to analyze the role of vocational high school in enhancing the competitiveness of Indonesia. Improving the quality of human capital through vocational education will eventually have implications in increasing competitiveness. Vocational education provides the opportunity for people to acquire practical skills, either to enter the job market and create employment or entrepreneurship. Furthermore, this paper will provide analysis of the significance of the solution in solving the problem empirically. At least, there are three main research problems that will be discussed in this paper: 1) Do SMK significantly affects economic development and regional competitiveness? 2) What are the potentials of SMK which can be used as opportunities to improve competitiveness? 3) What are the steps need to be taken to improve competitiveness through secondary education? The objectives of this paper are: 1) To assess Indonesiaâ&#x20AC;&#x2122;s competitiveness issues at the global level; 2) To assess the potential role of the vocational school as a manifestation of community empowerment through education; 3) To offer recommendations for addressing the problems related with competitiveness of the nation.

2. Method and Experiment Procedure Data and information are collected in the form of secondary data obtained from the internet, books, documents and results from previous research. The authors use quantitative data obtained from the websites of Central Bureau of Statistics (BPS): www.bps.go.id; Ministry of National Education Republic of Indonesia (Kemdiknas): www.kemdiknas.go.id; and Regional Autonomy Implementation Monitoring Committee (KPPOD): www.kppod.org. Relevant data on national competitiveness is

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obtained from the Global Competitiveness Report published by the World Economic Forum. Data analysis is conducted by using two methods, consist of quantitative and qualitative. Quantitative data were analyzed using descriptive analysis techniques to spot trends related intertemporal variables. Meanwhile, qualitative data were analyzed by the method of study of literature to produce a synthesis that became the basis of the appearance of ideas, conclusions and recommendations for solving research problems. Multiple regression analysis6 is also conducted to examine the effectiveness of proposed solutions in solving the problems. Multiple regressions are performed to see the significance of the number of vocational high school (SMK) graduates (as an independent variables) in influencing the gross regional income as a proxy of regional competitiveness provinces in Indonesia (dependent variable). Regression is performed using gross regional income (PDRB) data as the dependent variable and the number of graduates of secondary schools: junior high school (SMP), senior high school (SMA) and vocational high school (SMK), and also the provincial investment climate index as independent variables. Regression method chosen is ordinary least squares (OLS) method by using a cross-section data between provinces in Indonesia in 2008. Output is obtained and interpreted to determine the significance of the influence of independent variables on the variance of independent variables, and compare it with the existing theoretical basis.

3. Results and Discussion 3.1. Current Condition of Indonesiaâ&#x20AC;&#x2122;s Competitiveness and Secondary Education Based on the Global Competitiveness Report 2010-2011, it can be concluded that some pillars of Indonesiaâ&#x20AC;&#x2122;s competitiveness have low quality5. Some pillars are related to human resources and human capital, such as health and basic education, the quality of higher education and training, labor market efficiency, financial market development and technological readiness. Therefore, one of the steps that should be taken to enhance the quality of these pillars is to improve the quality of human resources itself.

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urrent Condition of Indonesia's Competitiveness and Secondary Education

on the Global Competitiveness Report 2010-2011, it can be concluded that some pillars of esiaâ&#x20AC;&#x2122;s competitiveness have low quality [5]. Some pillars are related to human resources and human l, such as health and basic education, the quality of higher education and training, labor market ncy, financial market development and technological Therefore, Participation of secondary education in Indonesiareadiness. is still very low. It can beone seenof the steps that d be taken to enhance the quality of these pillars is to improve the quality of human resources itself. clearly from Net Enrollment Rate (NER) data of Indonesia in 2003-2009 (see Figure 1).

Number of Participation

When compared with SD/MI SMP/MTS pation of secondary education in (elementary Indonesia school) is stilland very low. (junior It canhigh be school), seen clearly from Net ment Rate the (NER) data of in 2003-2009 Figure 1).school) Whenis compared with SD/MI enrollment rateIndonesia of SMA/SMK/MA (senior and(see vocational high much entary school) and SMP/MTS (junior high school), the enrollment rate of SMA/SMK/MA (senior and lower. onal high school) is much lower.

100,00 80,00 60,00 40,00 20,00 0,00 SD/MI

2003 2004 2005 2006 2007 2008 2009 92,55 93,04 93,25 93,54 93,78 93,99 94,37

SMP/MTs 63,49 65,24 65,37 66,52 66,90 67,39 67,43 SM/MA

40,56 42,96 43,50 43,77 44,84 44,97 45,11

Figure 1. Trend of Net Enrollment Rate (NER) in Indonesia 2003-2009 (in %) Figure 1. Trend of Net Enrollment Rate (NER) in Indonesia 2003-2009 (in %)

on the Global Competitiveness Report 2010-2011, the position of secondary education enrollment on the Global Report 2010-2011, position not of secondary f IndonesiaBased was ranked 95 inCompetitiveness the world of 139 countries. It isthe certainly surprising, given the low education enrollment rate of Indonesia was ranked 95 in the world of 139 countries. pation rates of secondary education (SMA/SMK/MA) in Indonesia (only 40.56 to 45.11%) during the is certainly surprising, given thethe lowquality participation rates of secondary education 2003-2009.ItBased on not previous research, of secondary education (especially vocational) in Indonesia (only 40.56 to 45.11%) the years 2003-2009. Based important (SMA/SMK/MA) factor for increasing competitiveness andduring economic development of Indonesia today. ding to Wicaksono, etresearch, al. (2010), high-quality vocational development is a response to encourage on previous the quality of secondary education (especially vocational) is donesian economy and take of competitiveness windows of opportunity [7]. In conclusion, increasing the one important factoradvantage for increasing and economic development pation of secondary particularly vocational (SMK), canvocational be considered as one of of Indonesiaeducation, today. According to Wicaksono, et al.school (2010), high-quality ays to improve the nation's and to the encourage economic in Indonesia. development is acompetitiveness response to encourage Indonesian economygrowth and take advantage of windows of opportunity.7 In conclusion, increasing the participation of

he Role of Vocational High School in Improving National Competitiveness: Analysis Result secondary education, particularly vocational school (SMK), can be considered as one of the ways to improve the nationâ&#x20AC;&#x2122;s competitiveness and to encourage economic

uthors recommend the government to enhance the role of vocational education in order to increase growth in Indonesia. al competitiveness. Increased competitiveness has significant impact on increasing productivity and ues. One indicator of prosperity and income in a particular region is regional gross domestic product 3.2 The Role of Vocational High School in Improving National Competitiveness: Analysis Result The authors recommend the government to enhance the role of vocational education in order to increase national competitiveness. Increased competitiveness

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has significant impact on increasing productivity and revenues. One indicator of prosperity and income in a particular region is regional gross domestic product (regional GDP). The greater the regional GDP per capita of a region then the welfare of society is increasing. The bigger the regional GDP may also indicate that the area has a high competitiveness. To support the explanation stating that the SMK is the solution to enhance competitiveness and promote economic growth, the authors conducted a multiple regression analysis to examine the significance of the number of SMK graduates (independent variables) in influencing the regional GDP provinces in Indonesia (dependent variable). Regional GDP variable here is a proxy for regional income, economic growth and competitiveness (improving the competitiveness will boost regional GDP). Number of junior high school (SMP) graduates and senior high school (SMA) graduates were also included as independent variables to identify and compare which one is more significant variable affecting GDP. The data used in this analysis is cross-section data between provinces in 2008 obtained from Kemdiknas and BPS. In addition, investment climate index8 is also included as independent variable to summarize other factors that influence regional GDP. Based on theory and research that have been described previously, the number of SMK graduates will more significantly affect GDP compared to other independent variables. There are two arguments to explain it. First, vocational graduates have higher skills and labor productivity so that more SMK graduates will have implications for the increasing competitiveness and regional economic growth. Second, vocational school graduates more easily absorbed by the labor market so that more graduates of SMK causes an increase in local revenue. To prove the validity of these arguments empirically, the authors performed multiple regression analysis with the following models: LN_Y_= β0+β1 LN_SMK_+β2 LN_SMA_+β3 LN_SMP+β4 INDEX where: Y

: regional gross domestic income (GDP) in 2008

SMK

: the number of graduates of vocational school year 2007/2008

SMA

: the number of high school graduates of the school year 2007/2008

SMP

: the number of graduates of junior academic year 2007/2008

INDEX : investment climate index (an index of total) in 2008

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Based on the results of regression analysis (see Table 1), can be seen that the above model has an R-squared of 0.794985. This means that 79.50% of variance in regional GDP can be explained by the number of SMK, SMA, and SMP graduates, and the investment climate index. These three independent variables have a positive correlation with the dependent variable, which means an increase in the number of SMK, SMA, and SMP graduates will increase regional income. This is in line with the theory of human capital. An increasing number of graduates of secondary schools indicate an increase in human capital that drives economic growth and increased revenue. Table Index Variable: LNY Method: Least Squares Date: 05/09/11 Time: 21:17 Sample: 1 33 Included observations: 33 Variable Coefficient C LN_SMK_ LN_SMA_ LN_SMP_ INDEX R-squared Adjusted R-squared S.E. of regression Sum squared resid Log likelihood F-statistic Prob(F-statistic)

6.085871 0.685143 0.354802 -0.058330 0.032239 0.794985 0.765697 0.637019 11.36221 -29.23242 27.14389 0.000000

Std. Error

t-Statistic

Prob.

1.579502 0.273626 0.712706 0.729094 0.020568

3.853032 2.503943 0.497824 -0.080004 1.567424

0.0006 0.0184 0.6225 0.9368 0.1282

Mean dependent var S.D. dependent var Akaike info criterion Schwarz criterion Hannan-Quinn criter. Durbin-Watson stat

17.07371 1.316024 2.074692 2.301436 2.150985 1.530108

Furthermore, it can be seen that the most significant coefficient LN_SMK_ than any other independent variables (with confidence intervals, Îą = 0.05), while the coefficient LN_SMA_, LN_SMP_ and INDEX are not significant. LN_SMK_ coefficient of 0.685143 indicates that an increase of 1% of vocational school graduates will lead to an increase/growth in regional GDP by 0.685%. These regression results are also consistent with previous discussion on a significant role of vocational high school in promoting competitiveness and economic growth.

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4. Conclusion Based on discussion and empirical evidence we can conclude that enhancing the role of SMK is the right solution to improve the nationâ&#x20AC;&#x2122;s competitiveness, and to promote regional economic growth. The strategy implementation should include three aspects. First, SMK has to accommodate regional economic development based on local potentials. Second, SMK has to promote entrepreneurship so that its graduates might be able to create employment in order to accelerate regional economic growth, and enhance the competitiveness of the regional economy. Third, SMK should play more significant role in empowering community by establishing a training center, skills development and community empowerment program which aims to provide short training for local citizen, empower local communities by establishing business units that employ local people and established a career center (career center) to increase labor market efficiency and reduce unemployment. Based on the results of regression analysis, it is proved that the number of SMK graduates most significantly affect regional GDP. This is also in line with previous explanation on a significant role in promoting competitiveness and economic growth. Based on discussion and empirical evidence we can conclude that enhancing the role of SMK can be considered as one of the ways to improve competitiveness and promote regional economic growth.

References 1. Sahlberg P. Education Reform for Raising Economic Competitiveness. Journal of Educational Change. 2006. 7: 259â&#x20AC;&#x201C;287.

2. ADB, ILO, IDB. Indonesia: Critical Development Constraints. Mandaluyong City: Asian Development Bank. 2010.

3. Kwiek M. Tertiary Education and Regional Economic Competitiveness and Innovation from a Central European Perspective. Budapest: Paper presented in OECD Thematic Review Seminar.

4. ADB. Education: Our Framework Policies and Strategies. Manila: Asian Development Bank. 2010.

5. WEF. The Global Competitiveness Report 2010-2011. Geneva: World Economic Forum. 2010.

6. Gujarati D N. Basic Econometrics. New York: McGraw-Hill Higher Education. 2002.

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7. Wicaksono P, et al. A Study on Labor Market Information based on Human Resources Potential in Indonesia. Depok: Paper presented in Research Day 2010 Seminar. 2009.

8. KPPOD, BKPM. Pemeringkatan Iklim Investasi 33 Provinsi di Indonesia Tahun 2008. Jakarta: KPPOD . 2008.

9. Firmanzah. Bisnis Global dan Daya Saing Indonesia. URL: http://metrotvnews. com/read/analisdetail/2010/08/19/63/Bisnis-Global-dan-Daya-Saing-Indonesia accessed on December 1, 2010.

10. KOMPAS.com. SMK Dukung Pembangunan Daerah. URL: http://dikdas.kemdiknas. go.id/content/berita/media/berita-568.html accessed on May 3, 2011.

11. Laksono, B.Y.G., et al. (2009, November). Studi Potensi Industri di Indonesia untuk Pengembangan SMK. Depok: Paper presented in Research Day 2009 Seminar. 2009

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PANDUAN PENULISAN Panduan Penulisan Naskah untuk Majalah Inovasi (font: Arial 12 points, bold) Nama penulis pertama1, nama penulis kedua2 (font: Arial 10.5 points, bold) Afiliasi penulis 1 (font: Arial 10 points)

Afiliasi penulis 2 (font: Arial 10 points)

E-mail: email@address.com (font: Arial 10 points, italic) Abstrak (font: Arial 10 points, bold) Abstrak harus ditulis dalam text box ini tidak lebih dari 200 kata. Isi abstrak antara lain ruang lingkup penelitian (apa yang akan anda sampaikan, ukuran, analisis dan lainnya), metode penelitian, hasil analisis dan kesimpulan secara singkat. Sertakan maksimal lima kata kunci untuk mempermudah pencarian.

1. Inovasi (font: Arial 10 points, bold) Majalah INOVASI (ISSN: 2085-871X) diterbitkan oleh Persatuan Pelajar Indonesia di Jepang (http://www.ppijepang.org/) sebagai berkala ilmiah semi-populer untuk menyajikan tulisan-tulisan berbagai topik, seperti sains dan teknologi, sosial, politik, ekonomi, pendidikan, dan topik humaniora lainnya. Majalah INOVASI berfungsi sebagai media untuk mengartikulasikan ide, pikiran, maupun hasil penelitian dalam rangka memperkaya wawasan dan khazanah ilmu pengetahuan. Website Inovasi: http://io.ppijepang.org/

2. Kategori artikel Majalah INOVASI menerima naskah baik yang bersifat ilmiah populer maupun ilmiah non-populer dengan kategori sebagai berikut:

2.1. Artikel populer Berisi tentang ide-ide atau gagasan baru yang dapat dimanfaatkan oleh masyarakat

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luas. Ditulis dalam bahasa Indonesia dengan ejaan yang disempurnakan (EYD) dan tidak lebih dari 6000 karakter atau maksimal 4 halaman.

2.2. Artikel non-populer Naskah asli yang belum pernah dipublikasikan dan tidak akan dipublikasikan di media lainnya. a. Maksimal 9000 karakter atau tidak lebih dari 6 halaman dan ditulis dalam bahasa Indonesia/Inggris. b. Judul harus menggambarkan isi pokok secara ringkas dan jelas serta tidak melebihi 14 kata. c. Struktur naskah terdiri atas Pendahuluan, Uraian Isi (metode, hasil dan diskusi), kesimpulan,

ucapan terima kasih dan daftar pustaka. Judul bab boleh

disesuaikan, misal: Bab 1 Perspektif Pertanian 5 tahun masa reformasi (mewakili pendahuluan)â&#x20AC;Ś dst. Huruf pertama setiap kata dalam judul bab harus ditulis dengan huruf kapital d. Pendahuluan berisi latar belakang/masalah, hipotesis, referensi yang relevan, pendekatan dan tujuan yang hendak dicapai. e. Uraian isi terdiri dari judul bab yang disesuaikan dengan kebutuhan dan informasi yang tersedia. Apabila naskah ini menyampaikan hasil penelitian yang khas, judul bab dalam uraian isi dapat terdiri dari Bahan dan Metode serta Hasil dan Pembahasan. f. Sangat disarankan jika dalam uraian isi/pembahasan bersifat kuantitatif. Misal: A lebih besar 10% daripada B, bukan A lebih besar dari B. g. Kesimpulan memuat secara singkat hasil yang telah diuraikan sebelumnya. Dapat dibuat dengan menggunakan penomoran atau pointer dalam satu paragraph.

3. Format penulisan artikel Ukuran kertas: A4; Margin atas: 3.5 cm; margin kiri, kanan dan bawah: 3 cm; tulisan: 1 kolom; spasi: tunggal; jenis huruf: Arial; ukuran: 10 points. Judul, nama penulis, afilisasi penulis dan alamat email ditulis dalam 1 kolom (center). Judul ditulis dengan font Arial, 12 points, bold, huruf kapital. Nama penulis ditulis dengan font Arial, 10.5 points, bold. Afiliasi penulis ditulis dengan font Arial, 10 points. Alamat email ditulis dengan font Arial, 10 points, italic. Satuan ditulis dalam unit satuan internasional (SI Unit) misalnya meter atau milimeter,

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kg atau gram, Newton dan lainnya. Pemisahan desimal untuk dimensi berat, tinggi dan waktu ditulis menggunakan titik (.) misalnya 3.4 m. Tanda koma (,) digunakan untuk memisahkan desimal pada besaran mata uang (misalnya : Rp 1,005,500,00)

4. Penulisan gambar/ilustrasi Gambar harus disertakan dengan resolusi tinggi supaya mempermudah pengamatan (format TIFF sangat disarankan). Gambar/Ilustrasi diberi nomor dan judul singkat. Sumber kutipan dicantumkan dengan jelas (jika gambar/ilustrasi merupakan hasil kutipan). Judul diletakkan di bawah gambar/ilustrasi dan ditulis dengan font Arial 9 points, center dan setiap kata diawali dengan huruf besar, kecuali kata-kata seperti, dan, atau, dalam, kata depan, yang, untuk. Gambar harus didiskusikan dalam teks utama (gambar berperan dalam mempermudah penyampaian gagasan dan paparan). Berikan warna biru untuk kata‘Gambar’di dalam teks untuk mempermudah pencarian.

Gambar 1. Kata “gambar” harus ditulis dengan huruf biru untuk memudahkan pencarian dari teks utama

5. Penulisan tabel Judul tabel diletakkan di atas tabel dan ditulis dengan font Arial 9 points, center dan ditulis mengikuti aturan seperti penulisan Judul Gambar. Catatan mengenai isi tabel (misal “sumber” atau satuan) dapat diletakkan dibawah tabel. Kata ‘Tabel’ juga diberi warna biru untuk mempermudah pencarian teks. Tabel 1. Kata “tabel” harus ditulis dengan huruf biru

Frekuensi

Standard Deviasi (cm/s)

(kHz) 76.8 104.6 205.1

N=10 6.723 3.375 2.418

N=12 4.751 2.112 1.869

Sumber: Inovasi Online

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6. Pengiriman naskah Naskah dikirim melalui elektronik mail dalam bentuk attachment file MS Word (*.doc atau *.docx) ke redaksi INOVASI yaitu editor.inovasi@gmail.com

Referensi Referensi diketik dengan menggunakan font 9. Referensi setiap sumber harus dirujuk dan disusun berdasarkan urutan pemunculan dalam naskah dengan menuliskan angka arab dalam format subscript tanpa tanda kurung, ditulis setelah tanda titik. Misalnya: “Majalah Inovasi merupakan majalah ilmiah yang diterbitkan PPI Jepang.1”

- Cara penulisan referensi dari majalah ilmiah Urutan penulisannya mulai dari nama pengarang (diakhiri tanda ”titik”), judul (diakhiri tanda ”titik”), nama majalah (diakhiri tanda ”titik”), tahun terbit (diakhiri tanda ”titik koma”), volume dan bila ada diikuti nomor (nomor ditulis dalam tanda kurung, tanpa spasi setelah volume, kemudian diakhiri tanda ”titik dua”), halaman (diakhiri tanda ”titik”). Penulisan nama pengarang dimulai dari ”nama akhir (nama keluarga)” diikuti inisial ”nama awal” dan bila ada inisial ”nama tengah” tanpa tanda ”koma” ataupun ”titik” di antara ”nama keluarga” dan inisial ”nama awal” maupun ” nama tengah”. Bila jumlah nama pengarah tujuh atau kurang, ditulis semua; tetapi bila lebih dari tujuh, maka cukup ditulis enam nama pertama diikuti kata ”dkk.” (bila artikel ditulis dalam Bahasa Inggris m aka ditulis ”et al.”). Contoh: 1. Bucchi A, Plotnikov AN, Shlapakova I, Danilo P Jr, Kryukova Y, Qu J, et al. Wild-type and mutant HCN channels in a tandem biological-electronic cardiac pacemaker. Circulation. 2006. 114(16): 992-999. 2. Cai J, Lin G, Jiang H, Yang B, Jiang X, Yu Q, Song J. 2006. Transplanted neonatal cardiomyocytes as a potential biological pacemaker in pigs with complete atrioventricular block. Transplantation. 81:1022-1026. 3. Sudaryanto A, Kartono M. Petun juk penulisan ilmiah. Inovasi Online. 2010; 9:6-9.

- Cara penulisan referensi dari buku Urutan penulisannya mulai dari nama pengarang (diakhiri tanda ”titik”), judul (diakhiri tanda ”titik”), nama buku (diakhiri tanda ”titik”), nama editor buku, dikuti

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kata ”(Ed.)” yang merupakan kependekan dari ”Editor” (diakhiri tanda ”titik”), nama kota penertbitan (diakhiri tanda ”titik dua”), nama penerbit (diakhiri tanda ”titik”), tahun terbit (diakhiri tanda ”titik dua”), halaman (diakhiri tanda ”titik”). Contoh: 4. Basuki A. Panduan penulisan untuk majalah ilmiah. Dalam: Strategi menulis. Suryanegara L, Junaidi B (Ed.). Jakarta: Gramedia. 2010: 16-20.

- Cara penulisan referensi dari laman internet Referensi yang berasal dari laman internet (website) harus menyertakan uniform resource locator (URL) dan tanggal referensi tersebut diakses. Nama judul artikel dan (bila ada) nama penulis dicantumkan. Contoh: 5. Maryadi J. Arsitektur Tradisional Ternate - Tidore dan Halmahera (Studi Analisa Konstruksi Tradisional). URL: http://busranto.blogspot.com/2007/04/arsitekturtradisional-ternate-dan.html diakses tanggal 10 Juni 2010. Contoh, bila artikel ditulis dalam Bahasa Inggris: 6. Arsitektur tradisional, perkembangan dan analisis. URL: http://busranto. blogspot.com/2007/04/arsitektur-tradisional-ternate-dan.html

accessed

June 10, 102010.

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Majalah Diterbitkan oleh Persatuan Pelajar Indonesia Jepang Website: http://io.ppijepang.org