Dynamic Mechanical properties and Glass Transition Temperature Analysis of Kevlar/Glass Fiber Epoxy

GRD Journals- Global Research and Development Journal for Engineering | Volume 2 | Issue 2 | January 2017 ISSN: 2455-5703

Dynamic Mechanical Properties and Glass Transition Temperature Analysis of Kevlar/Glass Fiber Epoxy Hybrid Composites R.Rangaraj Department of Mechanical Engineering Riyadh Ceramic, Saudi Arabia J.Prabakaran Assistant Professor Department of Mechanical Engineering Muthayammal Engineering College, Rasipuram

S.Gopal Assistant Professor Department of Mechanical Engineering Muthayammal Engineering College, Rasipuram

K.Kannan Assistant Professor Department of Mechanical Engineering Muthayammal Engineering College, Rasipuram

P.Ramesh Assistant Professor Department of Mechanical Engineering Muthayammal Engineering College, Rasipuram

Abstract In this paper an experimental demonstration were carried out on Kevlar/fiberglass composite laminates subjected to thermal properties. Epoxy based hybrid composites were prepared by hand layup followed by compression molding method. The Kevlar/fiberglass hybrid epoxy composites are manufactured at various ratio such as (50:50, 45:55, 40:60, and 35:65). The effect of epoxy resin on thermal properties was studied. The results showed that thermal properties such as Glass transition temperature, storage & loss modulus, Young’s modulus percentage of weight loss and fiber content of hybrid epoxy composites have been studied.

Keywords- Epoxy, Dynamic Mechanical properties and Glass Transition, Kevlar/fiberglass

I. INTRODUCTION Kevlar and glass fiber reinforced epoxy composites are widely used in a number of aerospace and non-aerospace applications. One of the most popular composite systems involves the combination of Kevlar fiber and epoxy resin. Glass fibers are better known for their, medium modulus, strength and stability, but are unsuitable for use in fatigue resistant composites, while glass fibers are characterized by high modulus, low density and superior thermal properties. The objective of this work therefore, is to study the effect, of fiber fraction on the thermal behaviour of composites containing, Kevlar and glass hybrid reinforcement in a bi functional epoxy resin system. The Thermo gravimetric Analysis technique (TGA) has been chosen and adopted to monitor the behaviour as it best represents the composites weight loss (which is mainly due to matrix loss) with temperature. The Hybrid composites of different fiber fractions were subjected to thermal degradation in a TGA furnace under nitrogen atmosphere to avoid any oxidation effects and respective thermo grams were recorded. Dynamic mechanical properties were employed to analyze the thermal behavior of hybrid composites.

To extend the burn off test protocol in ASTM D 3171-99 to the determination of the fiber and void contents of Kevlar/glass hybrid composites.

II. EXPERIMENTAL SETUP A. Material description Epoxy resin system chosen is LY55/HY951.Unidirectional reinforced epoxy composites were manufactured by stacking the pre impregnated (prepregs) layers into an compression mold, applying epoxy resin and curing at 80ºC for 120 min at 1500 kPa. The specimen square plate is 300 mm X 300 mm X 3mm.

B. Fabrication of hybrid composites To remove absorbed moisture, and prevent void formation, Kevlar and glass fiber were dried at 80°c for several hours before use.

The hand lay-up technique was used for the preparation in hybrid composites. They are various layers such as 12 and 10 layers.

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Dynamic Mechanical Properties and Glass Transition Temperature Analysis of Kevlar/Glass Fiber Epoxy Hybrid Composites (GRDJE/ Volume 2 / Issue 2 / 003)

The Kevlar and glass woven fabric were impregnated with epoxy resin and placed over the other in the compression molding. The mold was kept under pressure in 1500kpa for 20 min at 80°c to obtain partial curing of the resin. After the sample removed from mold and placed in atmosphere. For specimen were prepared in various ratios such as 35:65, 40:60, 45:55, and 50:50.

C. Method The characterization (determination of physical properties) of composites included determination of composite apparent density, weight content of fibers, of fibers and volume content of voids, void contents of the cured composites were measured according to ASTM D2734. The reinforcement weight fraction, Mf was determined by the resin burn-off technique.

Thermal properties of the samples were tested by dynamic mechanical analysis (DMA) and differential scanning calorimetric (DSC). DMA was carried out on a TA Instrument Dynamic Mechanical Analyzer 2980 at a heating rate of 3°C/min from 20 to 160°C and an oscillation frequency of 10 Hz. DSC experiments were performed in a DMA Q800 V20.9Build 27. DSC from TGA Instruments on 10–20 mg samples. The temperature was varied from 20 to 160°C at a constant heating rate of 3°C/min.

The analysis was performed under a nitrogen purge to prevent oxidation. The glass transition temperature is generally used for setting the curing conditions, because it is closely related to the degree of curing.

III. RESULTS AND DISCUSSION DSC curves of Kevlar and glass fiber composites can be seen in Fig.1 to 4. In the hybrid curves one brand endothermic peak was observed at 122.5°c for Kevlar and glass fiber commingled woven which corresponds to the glass transition temperature (Tg). The Tg of Kevlar textured woven was close to 112.3°C. DSC curves of Kevlar woven also indicated a sharp endothermic peak with the minimum at 122.5°C,139.7°C, 131.1°C and 127.7°C, respectively. Then from 122.5°c to 580°C, the DSC curves indicated an endothermic peak at a 10°C min-1 heating rate under a static air atmosphere. The DSC curves of Kevlar fibers showed an endothermic peak at 472.0°C, 511.9°C and 536.0°C respectively, before the melting point of Kevlar fiber. Only the Kevlar fiber possessed a glass transition temperature around 122.5°C with the decomposition of the Kevlar and glass fiber taking place immediately after melting. The DSC/TG curves of Kevlar fiber under a static air atmosphere and at a heating rate of -0.3 to 2.6 °C min-1. The kinematic parameters have been derived based on the peak temperature – program rate relation, or the so called non – isothermal techniques.

Fig. 1: DSC curves of Kevlar and glass fiber ratio 35:65

Fig. 2: DSC curves of Kevlar and glass fiber ratio 40:60

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Dynamic Mechanical Properties and Glass Transition Temperature Analysis of Kevlar/Glass Fiber Epoxy Hybrid Composites (GRDJE/ Volume 2 / Issue 2 / 003)

Fig. 3: DSC curves of Kevlar and glass fiber ratio 45:55

Fig. 4: DSC curves of Kevlar and glass fiber ratio 50:50

In all cases, storage modulus decrease with increase of temperature. At any particular temperature, storage modulus slightly increases with increase in volume fraction glass fiber and decrease with increasing temperature. Kevlar and glass the melting peak is shifted to high temperature region (92°C-98°C). As in the case of storage modulus, loss modulus of all the composites decreases with increasing temperature. It can also be noted that a slight increase in loss modulus is observed with increase in volume fraction of glass fiber at temperature range (0-160°C).

Sample: 1203005 a Size: 35.0000 x 12.7300 x 2.8900 mm Method: Temperature Ramp

File: C:...\Testing2011\1203005\1203005 a.001 Operator: TA Run Date: 23-Mar-2012 10:40 Instrument: DMA Q800 V20.9 Build 27

DMA

6000

800 106.13°C 0.3792

0.3

600

0.2

400

0.1

200

Loss Modulus (MPa)

4000

Tan Delta

Storage Modulus (MPa)

99.88°C 649.6MPa

2000

0 0

20

40

60

80

100

120

140

Temperature (°C)

0 160

Universal V4.5A TA Instruments

Fig. 5: DMA curves of kevlar and glass fiber ratio 35:65

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Dynamic Mechanical Properties and Glass Transition Temperature Analysis of Kevlar/Glass Fiber Epoxy Hybrid Composites (GRDJE/ Volume 2 / Issue 2 / 003)

Sample: 1203005 b Size: 35.0000 x 12.7800 x 2.7600 mm Method: Temperature Ramp

File: C:...\Testing2011\1203005\1203005 b.001 Operator: TA Run Date: 23-Mar-2012 12:57 Instrument: DMA Q800 V20.9 Build 27

DMA

10000

1400 92.03°C 1319MPa

1200

98.21°C 0.4184

8000

0.4

0.3 800

4000

600 0.2

Loss Modulus (MPa)

6000

Tan Delta

Storage Modulus (MPa)

1000

400 2000

0.1 200

0 20

40

60

80

100

120

0 160

140

Temperature (°C)

Universal V4.5A TA Instruments

Fig. 6: DMA curves of kevlar and glass fiber ratio 40:60

Sample: 1203005 c Size: 35.0000 x 12.7500 x 2.7900 mm Method: Temperature Ramp

File: C:...\Testing2011\1203005\1203005 c.001 Operator: TA Run Date: 23-Mar-2012 14:35 Instrument: DMA Q800 V20.9 Build 27

DMA

12000

1400 96.09°C 1351MPa

1200

10000

102.27°C 0.3181

0.3

6000

800 0.2 600

Loss Modulus (MPa)

Tan Delta

Storage Modulus (MPa)

1000 8000

4000 400 0.1 2000

200

0 20

40

60

80

100

120

140

Temperature (°C)

0 160 Universal V4.5A TA Instruments

Fig. 7: DMA curves of kevlar and glass fiber ratio 45:60

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Dynamic Mechanical Properties and Glass Transition Temperature Analysis of Kevlar/Glass Fiber Epoxy Hybrid Composites (GRDJE/ Volume 2 / Issue 2 / 003)

Sample: 1203005 d Size: 35.0000 x 12.7500 x 2.7900 mm Method: Temperature Ramp

File: C:...\Testing2011\1203005\1203005 d.001 Operator: TA Run Date: 23-Mar-2012 15:50 Instrument: DMA Q800 V20.9 Build 27

DMA

14000

2500 84.08°C 0.4714

12000

79.49°C 2096MPa

0.4

2000

0.3

1500

0.2

1000

0.1

500

6000

Loss Modulus (MPa)

8000

Tan Delta

Storage Modulus (MPa)

10000

4000

2000

0 20

40

60

80

100

120

Temperature (°C)

140

0 160 Universal V4.5A TA Instruments

Fig. 8: DMA curves of kevlar and glass fiber ratio 50:50

IV. CONCLUSION Almost all the measurements that can be done at different temperatures can be expanded into thermal analysis such as glass transition temperature and dynamic mechanic analysis can combined with various ratios such as 35:65, 40:60, 45:55, 50:50. From all results presented in this work, we can conclude that the hybridization of based composites with modified kevar/ glass fiber improves the thermal and increases the glass transition temperature without affecting the thermal stability. Considering the good properties of epoxy as low density and low cost, the interesting features reached with the fictionalizations of Kevlar fiber may be very useful for the development of higher performance composites with a thermal stability comparable to the epoxy-based composites.

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