IM1603 en

2016 volume 3

INNOVATIVE

MATERIALS

Translucent and photocatalytic concrete A cement free concrete canoe Plywood pavilion based on sea-urchin shells Fireproof hybrid wood Flax fibre reinforced polymer bridge deck

MATERIAL INNOVATION IN ENGINEERING, CONSTRUCTION AND INDUSTRIAL DESIGN

NEWS

CONTENTS

COLOFON About

Innovative Materials (Innovatieve Materialen) is a digital, independent magazine about material innovation in the fields of engineering, construction (buildings, infrastructure and industrial) and industrial design.

Innovative Materials is published in a digital format, although there is a printed edition with a small circulation. Digital, because interactive information is attached in the form of articles, papers, videos and links to expand the information available.

Scope

The digital edition is sent to engineers, scientists, students, designers, decision makers, innovators, suppliers and appliers working in civil engineering, construction, building, architecture, design, government and industry (both manufacturing industry and end users).

Innovative Materials has entered partnerships with several intermediate organisations and universities, all active in the field of material innovation.

More information (in Dutch): www.innovatievematerialen.nl

Publisher SJP Uitgevers Postbus 861 4200 AW Gorinchem tel. +31 183 66 08 08 info@innovatievematerialen.nl

Editor

Gerard van Nifterik

11 Translucent and photocatalytic concrete

Last year Rotterdam-based artist Jan Eric Visser was presenting a new outdoor project called ‘Ruins of Desire’. The sculpture pedestals are made of a new type of concrete developed by the University of Technology Eindhoven. In this new material, aggregates have been replaced by waste materials, such as glass waste. Also a mineral has been added to render the concrete self-cleaning and eliminate air pollution. Thus it uses UV light to prevent the growth of algae and degrade small particles in the air we breathe known as nitrogen oxides. Its performance is increased by 40 % as the various glass particles used in the concrete intensify the UV light.

14 A cement free concrete canoe

The Concrete Canoe Race is an annual event of the Betonvereniging, organized by a different College or University every year. Mostly civil engineering students participate. All participating teams build a canoe completely of concrete in which will be raced against each other over different distances. This year it took place on 27, 28 and May 29 in Presikhaaf park Arnhem, The Netherlands. Overall winner was the Leipzig team, but the team of Delft University has won two awards. Their concrete canoe weighed 250 kilos and was therefore the heaviest canoe of this year’s race. Most importantly, the team was given the award for most sustainable canoe because of the extraordinary material the canoe was made of: geopolymer concrete.

16 Plywood pavilion based on sea-urchin shells

The Institute for Computational Design (ICD) and the Institute of Building Structures and Structural Design (ITKE) of the University of Stuttgart have completed a new research pavilion demonstrating robotic textile fabrication techniques for segmented timber shells. The pavilion - so called ICD/ITKE Research Pavilion 2015-16 - is the first of its kind to employ industrial sewing of wood elements on an architectural scale.

18 Fireproof hybrid wood

For centuries, wood has been a popular light, solid building material.

Moreover, it is a renewable and easily recyclable raw material - with one drawback: wood burns. Until recently, building contractors were not allowed to erect residential and office buildings that were more than six floors high for reasons of fire safety. Scientists of EMPA and the Wood Materials Science Group at ETH Zurich, claim to have discovered a natural way to reduce the combustibility of wood.

20 Flax fibre reinforced polymer bridge deck

At Emmen Wildlife adventure park a movable bridge of flax fiber composite material was realised. In order to study the environmental impact of flax fiber reinforced plastic (VVVK) sandwich deck over conventional constructions, Windesheim has compared this deck to a glass fiber reinforced plastic (GVVK) sandwich, a traditional steel welded construction and a steel sandwich bridge deck.

Advertising & sponsoring

Drs. Petra Schoonebeek

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BERICHTEN NEWS

Mushroom building stones

Mushroom seats at UBC ‘bookstore’, Vancouver

Researchers from the University of British Columbia (UBC) in Vancouver, Canada, believe mushrooms could be used

widely for insulation and as a sustainable biodegradable structural building materials.

In an innovative design project, they developed six new stylish benches, grown from a blend of oyster mushroom spores and alder sawdust packed into moulds.

According to UBC, the project anticipate the emerging field of mycelium biocomposites, in which mushroom roots, or mycelium, grow in loose cellulosic material such as sawdust. The results are durable materials with attributes similar to that of polystyrene foams.

The sawdust and mycelium mix was shredded in a wood chipper, and then packed into moulds.

At UBC, researchers followed five steps in making the bricks.

More at UBC>

After five days, the moulds were removed and the blocks of mycelium biocomposite were wrapped in Saran wrap to encourage the growth of chitin (a strong polysaccharide similar to lobster shells) on their exterior.

After drying, the blocks were ready to be assembled into benches, and covered with clear acrylic.

First, alder sawdust was sterilized, blended with nutrients, and inoculated with the spores of Pleurotus ostreatus (oyster mushroom). The mycelium (mushroom roots) were left to grow in the sawdust for two weeks and then transferred to a greenhouse at UBC. Video

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NEWS

3D-printed foams age slowly

Flexible ceramics Based on technology developed at MESA+ Institude of Nanotechnology, Enschede, a new company Eurekite developed Flexiramics, a 100% ceramic material that is light and flexible like a polymer, but retains all the physicochemical properties of traditional ceramics.

The young professionals of Eurekite created the first ever flexible ceramic, which has the potential to serve as technology platform with applications in antennas, power electronics, harsh environments and fire safety. Eurokite developed a flexible ceramic PCB concept, merging the flexibility and lightweight of the polymer with the temperature stability and electrical insulation of a ceramic PCB.

Lawrence Livermore National Laboratory (LLNL) material scientists have found that 3D-printed foam works better than standard cellular materials in terms of durability and long-term mechanical performance.

Stability

Traditionally, foams are created by processes that lead to a highly non-uniform structure with significant dispersion in size, shape, thickness, connectedness and topology of its constituent cells. As an improved alternative, scientists at the additive manufacturing lab at LLNL recently demonstrated the feasibility of 3D printing of uniform foam structures through a process called direct-ink-write.

However, since 3D printing requires the use of polymers of certain properties, it is important to understand the longterm mechanical stability of such printed materials before they can be commercialized.

To address the stability question, the LLNL team performed accelerated aging experiments in which samples of both traditional stochastic foam and 3D-prin-

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ted materials were subjected to a set of elevated temperatures under constant compressive strain. This convincingly demonstrated that 3D-printed materials age slowly - better retain their mechanical and structural characteristics - as compared to their traditional counterparts.

Replacement

According to LLNL 3D-printing of foams offers tremendous flexibility in creating programmable architectures, customizable shapes and tunable mechanical response. Now that the results strongly indicates superior long-term stability and performance of the printed material, there is no reason not to consider replacing traditional foam with appropriately designed 3D-printed foam in specific future applications.

More at LLNL>

The material also shows promise as a substrate for electronics that can resist heavy duty applications, such as high temperature and high frequency. In addition Flexiramics substrates provide a greater number of design option and better signal integrity at a competitive price. www.eurekite.com>

NEWS

Wooden windows?

Windows and solar panels in the future could be made from one of the best and cheapest - construction materials

known: wood. Researchers at Stockholm’s KTH Royal Institute of Technology have developed a new transparent wood

material that’s suitable for mass production. The finding was recently published in the American Chemical Society journal, Biomacromolecules.

According to Lars Berglund, a professor at Wallenberg Wood Science Center at KTH, the optically transparent wood is a type of wood veneer in which the lignin, a component of the cell walls, is re­moved chemically. The white porous veneer substrate is impregnated with a transparent polymer and the optical properties of the two are then matched.

The transparent wood panels can be used for solar cells, windows and semitransparent facades, when the idea is to let light in but maintain privacy.

Among the work to be done next is enhancing the transparency of the material and scaling up the manufacturing process.

More at KTH>

‘Icephobic’ coating Researchers of the University of Michigan developed a durable, inexpensive ice-repellent coating, could make ice slide off equipment, airplanes and car windshields with only the force of gravity or a gentle breeze. According to the Michigan scientists this could have major implications in industries like energy, shipping and transportation, where ice is a constant problem in cold climates.

The new coating could also lead to big energy savings in freezers, which today rely on complex and energy-hungry defrosting systems to stay frost-free. An ice-repelling coating could do the same job with zero energy consumption, making household and industrial freezers up to 20 percent more efficient.

Made of a blend of common synthetic rubbers, the formula marks a departure

from earlier approaches that relied on making surfaces either very water-repellent or very slippery. The principle is based on the so called interfacial cavitation phenomena. Two rigid surfaces - for instance, ice and a car windshield - can stick tightly together, requiring a great deal of force to break the bond between them. But because of interfacial cavitation, a solid material stuck to a rubbery surface behaves differently. Even a small amount of force can deform the rubbery surface, breaking the solid free.

tance from the U-M MTRAC program, created to support new innovations that demonstrate high commercial potential.

More at UM>

The coating is detailed in a new paper published in the journal Science Advances. (‘Designing durable icephobic surfaces.’)

The team received funding and assis-

Video

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NEWS

Crystal House opened Stronger than concrete

Crucial part of the project was the development and testing of the glass stones.

Due to the sensitivity of the materials, an extremely high level of accuracy and craftsmanship was required and a technical development team was onsite throughout the process. Solid glass bricks were individually cast and crafted

by Poesia in Resana, near Venice. Research undertaken by the Delft University of Technology, in partnership with engineering firm ABT and contractor Wessels Zeist, led to the development of structural solutions and fabrication techniques, with the use of a high-strength, UV bonded, transparent adhesive from Delo Industrial Adhesives in Germany to cement the bricks together without the need for a more traditional mortar.

On april 19th, the doors of Crystal House, were officially opened. The entirely transparent façade of a highend flagship store on Amsterdam’s PC Hooftstraat, uses glass bricks, glass windows frames and glass architraves in a way to evoke the vernacular of the area with the goal to maintain the character of the site. The 620 m2 of retail and 220 m2 of housing, were designed for investor Warenar. The design unites the ambition of Amsterdam to have

large distinctive flagship stores without compromising the historical ensemble.

The project, conceptualised by MVRDV, was developed and constructed as part of a multi-team collaboration including Gietermans & Van Dijk Architects, Delft University of Technology, Brouwer & Kok engineers, ABT consulting engineers, Poesia (brand of Vetreria Resanese) glass manufacturers from Italy and contractor Wessels Zeist.

Despite its delicate looks, strength tests by the Delft University of Technology team proved that the glass-construction was in many ways stronger than concrete. The full-glass architrave, for instance, could withstand a force of up to 42.000 N. According to MVRDV the development of new construction methods unearthed additional possibilities for future building, such as the minimisation of waste materials. In essence, all of the glass components are completely recyclable.

The store is currently operated by French fashion house Chanel .

More at MVRDV>

Video

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NEWS

Meijs DenimX Motorman

After four years of research, renowned Dutch designer Marc Meijers discovered a spectacular way to make textile waste streams circular and process them into a variety of indoor and outdoor applications. With his new concept DenimX he creates high-quality lifestyle products from obsolete jeans for furniture, lighting, suitcase, helmet and automotive industries.

lifestyle market. The composition of the fibre reinforced material DenimX can be optimized to be as stiff, strong, light, thick or thin as required by the applica-

tion. The individual recycled fibres are visible and its visual qualities are pre­ served.

More at DENIMX>

Recipe

Discarded textiles represent little value for the fashion industry: upgrading these once-wasteful textiles into functional products is a process we call upcycling.

The industrial process is as simple as it is ingenious. In a nutshell: Meijers designed the DenimX recipe that combines recycled jeans fibers with bio-based plastics. With this composite material, three-dimensional products can be created. Trendy, solid and sophisticated.

Composition

DenimX is versatile in finish and composition. This makes it possible for DenimX to meet the aesthetic and technical requirements from clients within the

DenimX during the ‘Materials’, 20 and 21 april 2016 in Veldhoven, The Netherlands

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NEWS

DISCOVER : environmentally friendly roofing Wageningen UR Food & Biobased Research is working on a sustainable alternative to conventional roofing materials such as bituminous or synthetic roofing.

The goal is to develop a 100% biobased, environmentally friendly alternative that can compete with existing roofing products in terms of both price and quality.

Within it socalled ‘DISCOVER’-project (‘Development of Innovative Sustainable COVEring materials for Roofing) Wageningen UR Food & Biobased Research has teamed up with roofing manufacturer Icopal and Stichting DAKlabel.

Fossil

Bitumen and PVC are often used as the basis for roofing products because they give high-quality products with a long lifetime. The downside is that both bitumen and PVC are, like many other materials used in roofing products, made from fossil petroleum and their produc­ tion causes relatively high CO2-emis­ sions. An expected shortage of bitumen in the near future further underlines the need for a sustainable alternative.

Biomass

Wageningen Food & Biobased Research believes it is possible to develop a viable alternative made entirely from biomass.

The major technical obstacle is that biomass components are less waterproof and more reactive than bitumen. The research is aimed at finding ways to resolve this issue.

Substitutes

Several possible bio-based substitutes for bitumen, such as residues from agriculture and the paper industry, are taken as a starting point in the project.

The environmental impact as well as the impact of the various natural ingredients on key product requirements such as water resistance, durability, workability and strength will be investigated. A comparison of different compositions should

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ultimately lead to a recipe that yields the best performance and can be produced at the lowest cost and without any negative environmental impact. For this last purpose, an LCA will be conducted. The challenge is to develop a roofing material without having to change current production and application methods. Eventually, a prototype of a bio-based roofing membrane will be tested extensively as a demo-roof under out-door conditions.

The final product provides a sustainable alternative for roofers and will provide them an advantage in their projects where durability is always required.

BPM

The DISCOVER project is part of the large-scale research programme Biobased Performance Materials (BPM), aimed at developing high-quality materials based on biomass; materials that are being increasingly applied in practice.

The research focuses on two types of materials: polymers produced by plants, and polymers from biobased building blocks produced via biotechnology or chemical catalysis. The BPM programme is partly financed by the Top Sector Chemistry and is led by Wageningen UR Food & Biobased Research.

More at WUR> DISCOVER at www.icopal.nl> Also visit Lignine Platform WUR>

NEWS

Computational thermoforming Researchers at ETH Zurich and Disney Research Zurich have developed a new technique called Computational Thermoforming, by combining new software and an established industrial production technique called thermoforming. The method allows quick, cheap production of individual pieces or small batches of objects with structurally complex and colored surfaces.

Thermoforming is a common manufacturing process where a plastic sheet is heated to a pliable forming temperature, formed to a specific shape in a mold, and trimmed to create a usable product.

The technique’s core of ETH Zurich is based on an accurate simulation of the thermoforming process, which ETH doctoral student Christian Schüller developed in the Interactive Geometry Lab under the supervision of ETH Professor Olga Sorkine-Hornung.

The simulation computes an image from the coloured surface of a digital 3D model, which is then printed on to a plastic sheet. Through thermoforming, this sheet is then heated and forced into a three-dimensional shape. The key lies in computing the deformed image, so that the colours and patterns align perfectly

with the geometric details of the mould.

The researchers tested their technique with some very complex objects, including a Chinese mask and various modelmaking components, such as a car body shell and food replicas.

Video

The ETH Zurich scientists are convinced that the new method can be used in digital fabrication and industrial applications to mould prototypes before largescale production. Architectural firms and modellers could also benefit from this method to cheaply and quickly fabricate a 3D model based on their plans and visualisations.

The team will present their research at the 43rd International Conference and Exhibition on Computer Graphics and Interactive Techniques in Anaheim, California, July 24–28.

More at ETH>

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INNOVATIVE MATERIALS 3 2016

Translucent and photocatalytic concrete Last year Rotterdam-based artist Jan Eric Visser was presenting a new outdoor project called ‘Ruins of Desire’. The sculpture pedestals are made of a new type of concrete developed by the University of Technology Eindhoven. In this new material, aggregates have been replaced by waste materials, such as glass waste. Also a mineral has been added to render the concrete self-cleaning and eliminate air pollution. Thus it uses UV light to prevent the growth of algae and degrade small particles in the air we breathe known as nitrogen oxides.

Its performance is increased by 40 % as the various glass particles used in the concrete intensify the UV light.

Concrete is one of the most used materials in construction. The main reasons are its low price, high mechanical strength, high durability and variety of its form due to on-site casting or prefab design.

Unfortunately it is highly unsustainable in terms of CO2-emissions and resource efficiency. To make the concrete mixture more sustainable, aggregates can be replaced (partially or completely) by container waste glass. In research by the University of Technology Eindhoven, these products are incorporated in selfcompacting concrete (SCC) mixtures, replacing conventional aggregates and fine powders. The SCC mixtures were designed using a particle packing optimi-

zation algorithm in order to obtain good properties in both fresh and hardened states.

The addition of a photocatalyst was studied, to render the material self-cleaning and to promote photocatalytic oxidation (PCO) of NOx. This research was done by students Bart van Lieshout and Spiros Rouvas, coworkers dr. Dipl.-Eng. MSc.-Eng. Przemek Spiesz, dr. Qingliang Yu MSc., MSc. Xu Gao and prof.dr.ir Jos Brouwers, Eindhoven University of Technology, Faculty of the Built Environment, section Building Physics and Services.

ASR

In concrete some harmful reactions can occur, such as alkali-silica reactions (ASR) in which a formed gel expands over a longer period of time, damaging the concrete. Even though extensive research has already been done on the alkali-silica reaction issue in concrete, it is still not completely clear how this reaction takes place. Most of the proposed ASR mechanisms are based on the same principle: a reaction between the alkalis (Na2O and K2O) originating from the cement with silica originating from aggregates. As the product of this reaction, a gel of alkalisilicate is formed. This gel binds water and can expand to about twice its initial

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INNOVATIVE MATERIALS 3 2016 volume. This reaction only takes place if the amount of Na2O and K2O is high enough and when water is present.

Reactivity

Knowing how reactive different mixtures and materials are, is very important because the expansion can deteriorate concrete in the long term. Therefore, the application of low-alkali cements and/or non-reactive aggregates is crucial from the durability point of view. Different properties of materials used in concrete have an effect on the ASR reactivity. In the case of glass this comes to its par­ ticle size and chemical composition. For container waste glass, differences in ASR reactivity can be ascribed to different colors of the glass, i.e. different chemical compositions of the glass. Besides the composition, also the particle size plays a role in the reactivity of the glass. It is found that larger particles have higher long-term reactivity (deterioration ca-

pacity) than smaller particles. When particles smaller than sieve mesh #50 (ASTM) are used, the produced mixtures have very low reactivity. In general, the ASR is a very slow reaction (it can take years). When reactive fine materials (for instance glass powder) are added, a large reactive surface is available. The larger the area, the faster the reaction takes place and completes. If enough fine material (sufficient surface area) is available, the ASR can be finished before the hardening of concrete finishes. This means that the long-term expansion due to the ASR can be prevented.

Self-cleaning

Because of the TiO2-based photocatalytic oxidation (PCO) activated with the UV light, concrete may become a self-cleaning material. Additionally, if the right type of TiO2 is applied, concrete can be used as an active air purifying material in both outdoor (activated by the UV-light)

Jan Eric Visser, Untitled, 2015, IP 1, Translucent beton, Aquadyne and wood,105 x 34 x 28 cm. Photo: W. Vermaase

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and indoor (activated by the visible light) applications. Due to the applied glass, it might be possible that even more UV light is transferred to the TiO2 particles, making their activation more efficient and therefore this effect is also investigated by the TUE.

Results

Different mixtures were tested for their strength, alkali-silica reaction (ASR), translucency to the visible light and photocatalytic oxidation (PCO) properties.

Results show that the strength of the SCC mixtures containing the waste glass, compared to a reference mixture prepared with conventional aggregates and sand, is slightly lower in all the investigated mixtures, bur still very suitable for structural applications. With respect to ASR test results, mixtures with glass aggregates can be classified as highly reactive, but the glass powder can suppress the ASR.

Jan Eric Visser, Untitles (Ruins of Desire I) 2015, Translucent beton en Aquadyne, 100 x 24 x 22 cm. Photo: W. Vermaase

INNOVATIVE MATERIALS 3 2016

Translucent beton

The PCO test results show an improvement of the NOx degradation up to 40 % compared to the reference samples without glass particles. Finally, it is shown that the translucency of the product can be an attractive feature for concrete containing glass aggregates.

an innovative material produced of 100% postconsumer waste plastics. Micro and macro pores allow for the rooting of plants, even vegetables may be grown on it. The shapes were found as leftovers in the production machine and slightly adapted by the artist.

This article is based on the publication ‘Application of waste glass in translucent and photocatalytic concrete’: Van Lieshout, B.; Spiesz, P.; Brouwers, H.J.H., and Utilization of waste glass in translucent and photocatalytic concrete’’: Rouvas, S.,Spiesz, P.; Brouwers, H.J.H.

Showcase

According to the artist both materials embody the new aesthetics of a postindustrial future in which valuable resources will be cherished and no longer incinerated as ‘waste’. As such Ruins of Desire may be seen as a call for a new connection between man and matter, at the same time aspiring an artistic reconciliation of concept and matter.

Also visit Eindhoven University of Technology Building Physics and Services TUE>

The innovative, translucent concrete was applied and showcased for the first time

by Jan Eric Visser. He used the university’s standard test molds to cast pedestals as an initial step in the collaboration between artist and science. The sculptures in the project are made of Aquadyne,

More about Jan Eric Visser at www.janericvisser.nl>

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A cement free concrete canoe The Concrete Canoe Race is an annual event of the Betonvereniging, organized by a different College or University every year. Mostly civil engineering students participate. All participating teams build a canoe completely of concrete in which will be raced against each other over different distances. This year it took place on 27, 28 and May 29 in Presikhaaf park Arnhem, The Netherlands. Overall winner was the Leipzig team, but the team of Delft University has won two awards. Their concrete canoe weighed 250 kilos and was therefore the heaviest canoe of this year’s race. Most importantly, the team was given the award for most sustainable canoe because of the extraordinary material the canoe was made of: geopolymer concrete.

The canoe is made of geopolymer concrete, also known as cement free concrete. This relatively new material with concrete-like properties uses only industrial by-products as binder instead of the traditional Ordinary Portland Cement (OPC). This makes geopolymer concrete a sustainable alternative to traditional concrete.

Manufacturing OPC involves heating limestone in a kiln to form minerals which are grinded afterwards. These processes consume both energy and natural resources on a massive scale. The total CO2 footprint per one ton of Portland cement is almost 1:1, meaning that for each ton of Portland cement produced, one ton of CO2 is emitted.

In geopolymer concrete, on the other hand, OPC binder is replaced with a mixture of alkaline and industrial by-pro-

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ducts such as fly ash or blast furnace slag, which are produced during the manufacturing of, for instance, steel. Therefore, geopolymer concrete preserves natural resources, produces less CO2 and

allows us to use by-products to develop a sustainable construction material and to reduce our carbon footprint.

Delft researchers Marija Nedeljković, Mladena Luković and Ye Guang work

INNOVATIVE MATERIALS 3 2016 on sustainable concrete, suitable for the construction sector. According to Ye Guang, associate professor at the Microlab, concrete is the most utilised construction material on the planet and is allegedly responsible for 5% to 8% of all CO2 emissions. If geopolymers were used worldwide that would be great for the environment.

Furthermore, geopolymer concrete insulates and deals with heat better than traditional concrete. It is already used to manufacture fire-resistant tiles or walls.

Structural

So far the Delft scientists mostly focused on using geopolymer concrete in non-structural applications, says researcher Mladena Luković. This canoe is the first attempt at manufacturing a real structure. To ensure that it can carry loads and stay waterproof the team added fibers to the concrete mix. It worked out great and the students stayed dry during their first trial ride. The canoe is strong enough to race with!

Standards

However, the biggest issue is that there are no standards for application of geopolymer concrete and no rules or guidelines for structures made from it.

Ye Guang and his Geopolymer research group from the Microlab are therefore now working on a number of mixtures and are studying the durability and time-dependent behaviour of geopolymer concrete. Mladena from the Concrete Structures group is meanwhile looking for ways to use geopolymers in structural applications. This will allow the team to provide recommendations to industry partners so homes can finally be built from from geopolymer concrete.

TU Delft

Video

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INNOVATIVE MATERIALS 3 2016

Plywood pavilion based on sea-urchin shells The Institute for Computational Design (ICD) and the Institute of Building Structures and Structural Design (ITKE) of the University of Stuttgart have completed a new research pavilion demonstrating robotic textile fabrication techniques for segmented timber shells.

The pavilion - so called ICD/ITKE Research Pavilion 2015-16 - is the first of its kind to employ industrial sewing of wood elements on an architectural scale.

The development of the ICD/ITKE Research Pavilion 2015-16 is based on the biomimetic investigation of natural segmented plate structures and novel robotic fabrication methods for sewing thin layers of plywood. The project was realized by students and researchers within a multi-disciplinary team of architects, engineers, biologists, and palaeontologists.

It commenced with the analysis of the constructional morphology of sea urchins, sand dollars in particular. At the same time, a fabrication technique was developed that enables the production of elastically bent, double-layered seg-

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INNOVATIVE MATERIALS 3 2016 ments made from custom-laminated, robotically sewn beech plywood. Introducing textile connection methods in timber construction enables extremely lightweight and performative segmented timber shells.

Structures

Previous studies on sea urchins already led to the transfer of constructional principles and the development of new construction methods for timber plate shells. In this project, shell structures were further analysed in an interdisciplinary cooperation between engineers at Stuttgart University and biologists from Tubingen University. It was concluded that the performance of these segmented lightweight structures relies not only on the arrangement of its individual calcite plates, but also on the geometric morphology of a double layered system and the differentiation within the material. Most importantly however, the calcite plates of some sea urchin species are connected through fibrous elements in addition to the finger joints, and it can be hypothesized that this multi-material connection plays an important role in maintaining the integrity of the sea urchin’s shell during growth and exposure to external forces.

Robotiv sewing

The pavilion consists of 151 segments that were prefabricated by robotic sewing. Each of them is made out of three

individually laminated beech plywood strips. Ranging between 0.5 and 1.5 m in diameter, their specific shapes and material make-up are programmed to fit local structural and geometrical requirements. The textile connections developed for this project allow overco-

ming the need for any metal fasteners.

The entire structure weighs 780 kg while covering an area of 85 m² and spanning 9.3 meters.

Posibilities

According to ICD/ITKE , the research pavilion shows how the computational synthesis of biological principles and the complex reciprocities between material, form and robotic fabrication can lead to innovative timber construction methods.

This multidisciplinary research approach does not only lead to performative and material efficient lightweight structure, it also expands the tectonic possibilities of wood architecture.

ITKE Stuttgart>

Video

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Fireproof hybrid wood For centuries, wood has been a popular light, solid building material. Moreover, it is a renewable and easily recyclable raw material - with one drawback: wood burns. Until recently, building contractors were not allowed to erect residential and office buildings that were more than six floors high for reasons of fire safety. Scientists of EMPA and the Wood Materials Science Group at ETH Zurich, claim to have discovered a natural way to reduce the combustibility of wood.

The process of the EMPA and ETH-Zurich research team protects the wood from flames by depositing calcium carbonate (limestone) in the wood’s cell structure, mineralizing the wood, in other words.

The knack is to get the mineral deep into the structure of the wood.

In order to achieve the desired effect, the researchers soak the wood in an aqueous solution containing carbonic acid dimethyl ester and calcium chloride - a salt that dissolves readily in water, just like liquid ester. Once the wood has been soaked with the mixture right through to the cells, the researchers increase the pH value by adding caustic

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Valcinated wood cells

INNOVATIVE MATERIALS 3 2016 soda lye until the solution turns alkaline.

Once the mixture has reached a certain pH value, the molecule breaks down into alcohol and CO2. The latter begins to react with the calcium ions in the solution and binds with calcium carbonate, which accumulates deep inside the cell structure.

According to prof. Ingo Burgert, who also runs the Wood Materials Science Group at ETH Zurich, the team of researchers take their inspiration for the development of such organic-inorganic materials from nature. Evolution has yielded a whole series of these so-called hybrid materials, like seashells, teeth, mother-of-pearl or bone.

Several fire tests conducted by the workgroup produced promising results.

Thanks to the limestone in the cell structure, the researchers were able to reduce the wood’s combustibility by about a third. The mineralized wood displays many other advantages besides good fire resistance. Both wood and calcium

carbonate bind CO2 inside them, which is very interesting from an environmental perspective. The researchers point out that they did not use any hazardous substances during production or in the end product. Recycling the hybrid wood is therefore harmless, unlike normal wood, which is treated with flame-retardant chemicals using conventional methods.

Moreover, conventional fire protection is often applied to the wood externally.

Whereas these surface coatings can come away over time, in hybrid wood the fire protection is embedded deep inside the construction material.

More at EMPA>

Glow in the dark cement

A Mexican scientist - Dr. José Carlos Rubio, Mexico’s Michoacan’s University of San Nicolas Hidalgo (MSNH) - has created glowing cement that absorbs solar energy during the day and emits light after sun-down, up to 12 hours. The material - patented by MSNH - could make

roads and structures glow in the dark, cutting the cost of street-lighting. While most fluorescent materials are made from polymers and have an average of life span of three years under harsh UV rays, this new cement is uv-resistant and will last 100 years, according to Rubio.

The research is in its commercialisation stage, with its inclusion in plaster and other construction products also being explored.

More at Investigación y Desarrollo>

19 | INNOVATIVE MATERIALS 3 2016

INNOVATIVE MATERIALS 3 2016

Research on technical durability

Flax fibre reinforced polymer bridge deck At Emmen Wildlife adventure park a movable bridge of flax fiber composite material was realised. In order to study the environmental impact of flax fiber reinforced plastic (FFRP) sandwich deck over conventional constructions, Windesheim has compared this deck to a glass fiber reinforced plastic (GFRP) sandwich, a traditional steel welded structure and a steel sandwich bridge deck.

Flax fibre reinforced polymer (FFRP) is being introduced in civil structures. Designing such structures durable requires information about reduction of strength, stiffness and cross section. For FFRP the reduction factors for mechanical properties by moisture, temperature, creep and fatigue have been studied. Also the degradation by UV, wear, chemicals and rot have been studied. This is conducted through literature study and by accelerated moisture tests. For the pioneering project ‘Bio-bridge Wildlife Adventure Park Emmen’ reduction factors and actions against section reduction are advised.

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Glass fibre composite: increasingly known territory

The strength and E-modulus of composites are usually determined at 20°C under room-dry conditions during which specimens are tested in a single and quick load towards rupture.

Taking into account the environmental circumstances and load effects on the strength and stiffness of composites, conversion factors ηc•are used. For Glass Fiber Reinforced Polymer (GFRP) four different conversion factors exist 1) temperature 2) humidity 3) creep & 4) fatigue of E-modulus [1].

ad 1) the GRFP temperature in western Europe fluctuates from about -20°C to +80°C. For GFRP a factor of 0.9 for both strength and modulus is prescribed in most cases. ad 2) depending on the application ‘always dry’, ‘dry & wet’ and ‘always wet’ for GFRP a factor of 1.0, 0.9 resp. 0.8 for both strength and modulus is prescribed. ad 3) depending on the type of fibre fabric i.e. ‘straight’, ‘woven’ and ‘mat’ for GFRP a factor t-0,01, t-0,04 resp. t-0,10 is prescribed with t in hours, for

INNOVATIVE MATERIALS 3 2016 In the absence of appropriate literature the conversion factors for humidity and temperature were determined experimentally. Since it was expected that the degradation mechanisms for FFRP (except rot) can be dealt with using the same measures as for GFRP, this was studied using literature review and expert interviews.

Table 1 Properties of flax fibres and E-glass fibres

both long term strength and modulus (creep). For straight / unidirectional (UD) / non-crimp fibre fabrics, this gives a factor about 0.87 after 100 years, and only fibres in the load direction contribute. ad 4) the E-modulus reduces with load cycles. For GFRP for stiffness and stability (FEULER also depends on E) a factor of 0.9 is prescribed. Fatigue strength is dealt with separately.

GFRP bridge decks can be realised in which fibres and matrix cooperate so well together that a life time 50 to 100 years or even longer is got. This requires among others an appropriate resin, a compatible sizing on the fibres and an careful execution of the structure. Sandwiches with a light weight foam core between GFRP faces are often used to optimize the use of materials.

It is common for GFRP bridge decks to apply a wearing layer at the top side and a coating on the other outer sides, this for roughness resp. esthetical reasons.

These polymer layers provide improved weathering behaviour for the overall GFRP structure as well.

Flax fibre composite: developing territory

For the design of GFRP structures the above mentioned conversion factors are widely used. For FFRP Windesheim has studied these factors, to use them for the design of the first ever bridge deck in flax. In order to design a durable structure conform Eurocode NEN-EN 1990 the degradation mechanisms wear, UV, chemicals and rot are also studied. Goal of this study was to design a movable pedestrian bridge with an FFRP deck for the new Wildlife Adventure Park at Emmen (NL). Flax fibres appear to be ideal for this application (see table 1), this is because flax fibre reinforcement: - has a much lower density than glass fibre and the deck has no counter weight; - is almost as stiff as glass fibre and deflection in bridge decks is often decisive; - would have lower environmental impact than glass fibre, since it binds CO2 by growing instead of emits it by producing; furthermore FFRP can be completely thermally recycled.

In GFRP bridges several plies of UD fabrics are applied to form the laminate, because straight fibres have a minimum of creep. Furthermore composites with UD are stiffer and have a significant larger strain at rupture. The FFRP study therefore focused on UD fabrics. The scope of the study was further limited to non-conditioned and non-chemically treated flax fibres, to accommodate the starting points for the bridge deck as production friendly resp. environment friendly.

Research methods

For light weight FFRP pedestrian bridges dynamic modulus and strength (fatigue), creep and long term strength are less relevant. These aspect are studied by literature review only therefore.

Figure 1 Bridge impression

Results literature study Conventional degradation The fibres are protected by the matrix, and extra protected by a coating. Degradation by UV-radiation, wear and chemicals is for FFRP not essentially different as for GFRP bridge decks. FFRP is equal sensitive for high temperatures as GFRP, as matrix degradation starts below 180 °C at which flax fibre degradation starts.

Degradation by micro-organisms Rot-degradation by micro-organisms (bacteria, fungi and such) under humid conditions- is the distinctive degradation mechanism for FFRP. Rot requires the availability of micro-organisms, oxygen, moisture and other substances like nitrogen. An effective solution for this problem is to disable all micro-organisms, for example by a steam treatment of the flax fibres [4]. A specific steam treatment -Duralin- makes the flax composite even a bit stronger, stiffer and makes it absorb less moisture, furthermore retting of flax stems to technical flax bundles is not required any more [5].

Conversion factor for creep (Ρcc) Quantitative information for FFRP is not found in literature. According to the supplier of flax fibres the expected time effect can be estimated by looking at timber structures, since both are cellulose fibres. Therefore in table 2 long term factors have been taken from timber structures.

For the long term strength the Eurocode Timber distinguishes reduction factors kmod for very short, short (<1 week), middle long (1 week-6 months), long (6 months-10 years) and remaining (>10 years). The factor kmod varies from 0.5 resp. 0.6 at remaining loads to 1.1 for very short during load like wind or

21 | INNOVATIVE MATERIALS 3 2016

INNOVATIVE MATERIALS 3 2016

explosion. A factor 1.0 belongs to the prescribed test duration of 5±2 minutes.

The reduction factor for RH<85% (and RH<65%) can be expressed in the formula t-0,04 with t in hours.

Conversion factor for dynamic load (ηcf) [7]

differs. Therefor the curves are normalized, i.e. the fatigue strength is divided by the ultimate static strength. In normalized graphs the bio-fibres results are everywhere in between curves for glass and carbon fibres. For flax fibres the static strength can be taken as a starting point for the fatigue line, for the slope

the same slope as for glass fibres can be taken.

Conversion factors for temperature and humidity (ηct & ηch) The conversion factors for humidity and temperature for FFRP are derived from experiments after full saturation of the FFRP.

Experiments [9]

Table 2 Long term factors timber structures[6]

In figure 2 E-n curves for flax fibre reinforced epoxies with various fabrics (UD, woven, mat) are shown. For UD-FFRP lamella the E-modulus increases after 10-100 cycles, but after 10,000 cycles it returns to the original level. The fibres apparently straighten in the first cycles and only later ‘fatigue’ or ‘dynamic modulus’ is able to manifest itself. In UD-FFRP laminate the plies with fibres in transversal direction appear to reduce the total stiffness directly. The reduction of the E-modulus is a factor of about 0.9.

Fatigue [8] The results of fatigue tests for flax fibre reinforced epoxies with various fabrics are shown in σ–n curves. The shape of these curves are difficult to compare because the static strength for n=1 cycle

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(Below) Figure 2 E–n curves of various flax-epoxy composites Adopted from [7] © JEC Composites

For FFRP flexural tests were carried out according to ISO 14125 on UD flax laminates with a variation in temperature and humidity. The laminates consisted of 6 layer of UD flax fibres AmpliTex 5009 of Bcomp® in one direction. As resin DSM’s vinyl ester (VE) Atlac® 430 was applied.

INNOVATIVE MATERIALS 3 2016

Figure 3 FFRP moisture absorption m/m vs. time for RH=80% & T=20°C (0%= oven-dry)

Atlac | flexural strength 0° 450 40°C ≤ T ≤ 80°C 5% ≤ RH ≤ 15% 400 350 ‐20°C ≤ T ≤ 20°C 30% ≤ RH ≤ 50%

Flexural strength (MPa )

300

T = 20°C RH = 80%

250

η௖் ൉ η௖ு = 0,78

200

‐20°C 5°C 20°C

η௖் ൉ η௖ு = 0,49

40°C 60°C

150

80°C T20RH80

20°C ≤ T ≤ 80°C RH =100%

100

Results of the experiments [9]

50

In figures 4 the strength and modulus in N/mm2 of oven-dry, room-dry, RH=80% and full-wet conditions are depicted against weight increase by moisture uptake.

0 ‐4,0

‐2,0

0,0

2,0

4,0

6,0

8,0

10,0

12,0

14,0

16,0

Moisture absorption (%)

Atlac | flexural modulus 0° 30000 40°C ≤ T ≤ 80°C 5% ≤ RH ≤ 15%

Flexural modulus (MPa )

25000

‐20°C ≤ T ≤ 20°C 30% ≤ RH ≤ 50%

20000

T = 20°C RH = 80%

15000

‐20°C

η௖் ൉ η௖ு = 0,85

5°C 20°C η௖் ൉ η௖ு = 0,26

10000

40°C 60°C 80°C

20°C ≤ T ≤ 80°C RH =100%

T20RH80

5000

0 ‐4,0

‐2,0

0,0

2,0

4,0

6,0

8,0

10,0

Hardened with AKZO Nobels cobalt-free, Blucure accelerator system Nouryact® CF 12 N. Because hardening of vinyl and polyester resins with standard cobaltperoxides does not work under humid conditions [10], the by DSM and AKZO Nobel developed cobalt-free BlucureTM hardening systems was applied. All test specimen were post cured at 40°C. The tested panels were sealed at the sides.

The dimensions of the specimens were 75x15x ̴3.5mm, the span was 50mm.

All test were repeated 3 times (n=3), on specimens with fibres in parallel direction (0°) and on fibres in transversal direction (90°). Of the three values the average was determined. The variations in temperature were 2 ­ 0°C, 5°C, 20°C, 40°C, 60°C and 80°C. These temperatures were combined with water submerged specimen (RH= 100%), other variations were oven-dry (RH= 10±5%) with 40°C, 60°C en 80°C, and room-dry (RH= 40±10%) with -20°C, 5°C and 20°C . Every 200 hours specimens were tested, the moisture content was determined and it was determined if the humidity equilibrium was reached. For the RH= 80% at 20°C specimens only the moisture content was determined at the intermediate, and only at humidity equilibrium the mechanical properties in the direction of the fibres were determined.

12,0

14,0

16,0

Moisture absorption (%)

Figures 4 FFRP flexural strength & modulus vs. moisture absorption m/m in various conditions for VE resin

The test values at about 20°C and about Relative Humidity RH=40% were taken as reference value: 0% moisture uptake. RH= 80% was taken as a good approximation of the average weather conditions outside in the Netherlands: alternating wet & dry. The encircled values are the values where full saturation is reached, for lower temperatures that happens after months of testing. The values that are not encircled are intermediate values for underwater specimens.

Here the fibres in the outer layers will contain more moisture than the inner layers. For RH=80% and RH=100% the combined conversion factors for temperature and humidity after full saturation are appended.

23 | INNOVATIVE MATERIALS 3 2016

INNOVATIVE MATERIALS 3 2016

In figure 3 the time course is depicted of the weight increase by moisture uptake at RH= 80% for FFRPs. After about 3 months the equilibrium moisture content was reached at 20°C. Underwater tests show that the point of full saturation is reached far sooner at higher temperatures. Tests on specimens that were oven-dried showed a moderate increase in mechanical properties (see figures 4). Tests on specimens that were kept underwater until full saturation occurred and were oven-dried afterwards show comparable mechanical properties as tested under room-dry conditions.

Interpretation of experiments and discussion [9] Temperature influence: dry test only From the dry tests it appears that as conversion factor for temperature 0.9 can be applied for FFRP.

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Humidity influence: from accelerated tests to the long term

Irreversibility: from one wet-dry cycle test to more cycles

For RH= 80% applies: the combined reduction for temperature and moisture at full saturation is about 0.8 for both strength and stiffness (see figures 4).

The conversion factor for moisture only therefore becomes 0.8/0.9 = 0.9, without the degradation after full saturation. Degradation after full saturation is included by multiplying the determined conversion factor for humidity with the conversion factor for humidity in GFRP. This is based on the hypothesis that the first factor is caused by the moisture expansion in the flax fibres till saturation occurs and the second factor by long term moisture related degradation of the matrix. Therefore the total FFRP conversion factor as suggested for this project becomes: 0.9 x 0.9 = 0.8 (RH= 80%).

The moderate reduction in mechanical properties after the first fully saturated – fully dried cycle, indicates a starting detachment. The results of the mechanical properties of wet specimens perpendicular to the fibre direction support this. In figure 5 the detachment process is visualized.

Literature shows that that cycles based on fully-saturated – fully-dried reduce the mechanical properties from moderate after the first cycle (as well) to dramatically after a few cycles. [12]

For underwater tests the detachment between fibres and matrix is far too much when saturation occurs.

Conclusions

Degradation of FFRP by UV-radiation, wear and chemicals is in essence not different to GFRP. Degradation by micro-organisms in humid circumstances is the distinctive degradation mechanism.

Compared to GFRP the mechanical properties of FFRP are reduced dramatically in underwater circumstances. Application herewith is unrealistic.

INNOVATIVE MATERIALS 3 2016

A safe approach is to take the slope of fatigue curves as determined for GFRP as the slope for FFRP.

Implications and advices

For the application of unconditioned, chemically untreated UD flax fibres in FRP structures in outside conditions with

an average humidity of RH= 80%, it is advised to: a) give the flax fibres a steam pre-treatment. This will disable micro-organisms and therefore prevent rot; b) select or develop a resin that gives good bonding with flax fibres, preferably without sizing. The tested AtlacÂŽ resin gives an acceptable bonding for RH= 80%; c) apply a cobalt-free hardening resin. A cobalt accelerator becomes inactive in the presence of water in un-dried flax fibres; d) protect the FFRP structure with a polymer layer all around and assure proper drainage. Guarding the structure from outside humidity fluctuations ensures limited fluctuations of water uptake in the fibres. Moreover it protects against UV-radiation, wear and chemicals;

Figure 5 Effect of saturation and drying on fibre-matrix interface (Adopted from [11]. (By permission from Univ. of South. Queensland)

25 | INNOVATIVE MATERIALS 3 2016

INNOVATIVE MATERIALS 3 2016 In table 3 the advised factors for the flax-FRP project and those for GFRP in general are shown.

The table is composed for: - vinyl ester resin Atlac® 430, hardened with cobalt free Nouryact®, or equal; - non conditioned, non-chemically treated flax fibres AmpliTex or equal; - UD/straight fibre fabrics (not woven or mat fabrics).

Further recommendations

I) It is recommended to perform long term research (>10 years) on the degradation upon climate fluctuation of un-coated FFRP both steam pre- and non-treated flax fibres. Next to that monitoring of the first FFRP bridge deck is recommended. With the results of these additional studies it can be decided to what extent it is necessary to keep a coating perfectly intact during the full lifetime.

II) Before FFRP start being applied for structures with a significant amount of remaining load, it is recommended to study the long term effects of FFRP. III) The application of FFRP in permanently submerged structures is not yet recommended. For this application further research and development is needed.

Ir. P.G.F. Bosman, lecturer civil engineering, researcher PPE Windesheim Univ. of Appl. Sciences Ing. P. Schreuder, junior researcher Professorship for Polymer Engineering (PPE) Windesheim

References: [1] Klamer E e.a., Long-term effects of wet an outdoor conditions on GFRP, 2015 & CUR Recommendation 96, Fibre Reinforced Polymer in civil structures (in Dutch), 2016.

2] Oever van den M e.a., Bio-composites, Natural fibres and bio-resins in technical applications, Wageningen University (in Dutch), 2012.

[3] Duigou Le A. e.a., Environmental Impact Analysis of the production of flax fibres to be used as composite material reinforcement, Journal of Biobased Materials & Bioenergy 5, p1-13, 2011.

[4] Dicker MPM, Green composites: A review of material attributes and complementary Applications, Composites Parts A: Applied Science and Manufacturing 56, p280-289, 2014.

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Table 3 Advised UD-conversion factors for the FFRP-project

[5] Wingerde AM e.a., Bladeco Windturbine blades of ecological materials (in Dutch), 2002 & Bismark A e.a., Surface Characterization of Flax, Hemp and Cellulose Fibers; Surface Properties and the Water Uptake Behavior, 2002.

Professorship

[6] EN 1995-1 Eurocode 5: Design and calculation Timber structures, 2005.

The professorship of Polymer Engineering of the University of Applied Sciences Windesheim has hybrid design, sustainability and composite applications among others as her focal points. Together with (regional) companies and students practice-oriented research is carried out, that possibly leads to innovations and contributes to education in the broadest sense of the word. This project is a good example of that.

We thank Aliancys Resins Zwolle, Composite Technology Centre Hengelo, Machinefabriek Emmen and University of Applied Sciences Stenden for their cooperation in this research.

[7]Bensadoun FK, Fatigue Behaviour of flax reinforced composites, Technical book JEC/CELC Flex and Hemp fibres: a natural solution for the composite industry Add-on release p35-36. 2014.

[8] Shah DU e.a., Fatigue life evaluation of aligned plant fibre composites through σ-N curves and constant-life diagrams, Composites Science and Technology p.139-149, 2013.

[9] Bosman PGF et al., Bio-composite bridge deck – research to long term behaviour (in Dutch).

Professorship of Polymer technology, University of applied science Windesheim, Feb 2015.

[10] Dijk van C, Removing barriers for bio-based composites production with novel water-insensitive cure systems Reinforced Plastics 59(1) p52-55, Feb 2015.

[11] Azwa ZN e.a., A review on the degradability of polymeric composites based on natural fibres, Materials and Design 47 p424-442, 2013.[12] Newman RH, Auto-accelerative water damage in an epoxy composite reinforces with plain-weave flax fabric. Composites: Part A 40, p1615-1620, 2009.

[13] Dhakal HN et al., Effects of water immersion ageing on the mechanical properties of flax and jute fibre biocomposites evaluated by nanoindentation and flexural testing. Journal of Composite Materials, 48(111) p1399-1406, 2014.

For this project the author made use of research subsidy under the Dutch top sectors policy: this research has was made possible by GreenPAC, an initiative of Stenden and Windesheim for research in the field of polymer applications in the North-East Netherlands.

INNOVATIVE MATERIALS The magazine started a few years ago and provides news about innovative materials or the innovative use of materials. The idea is that an ever increasing demand leads to a constant search for better and safer products as well as methods to save materials and energy. Enabling these innovations is crucial, not only to be competitive but also to meet the challenges of enhancing and protecting the environment in terms of durability, C2C and the carbon footprint. By choosing smart, sustainable and innovative materials, constructors, engineers and designers obtain more opportunities to distinguish themselves.

Innovative Materials wants to help them achieve this by connecting supply and demand.

Innovative Materials has entered partnerships with several intermediate organisations and universities, all active in the field of material innovation.

INNOVATIVE MATERIALS Innovative Materials is published in a digital format, although there is a printed edition with a small circulation. Digital, because interactive information is attached in the form of articles, papers, videos and links to expand the information available.

There are two editions. The free one is a non-printable magazine, published online. In this version the interactive links are limited. Subscribers with a paid subscription will receive full access to both the digital edition and an interactive PDF, with links to all the extra information.

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