Biocomposites Flax for
Biocomposites Flax for high-tech applications High Vibration in carbon Damped Vibration thanks to FlaxPly Shock, Impact, Force Carbon layer FlaxPly Carbon layer Flax fibres are offering the best mechanical properties on the natural fibres market and are thus increasingly used as an environmentally friendly reinforcement for different applications. Their specific properties, which are higher than those of glass fibres, come in combination with interesting cost and weight reductions. Since flax fibres are easily and massively available near the facilities of Lineo NV (St Martin du Tilleul, France), the company is focused on the use of flax fibre for the development of its products. “We found that low environmental impact is not the only advantage of flax fibres. Their intrinsic technical properties can also make significant contributions to improving the performance of the finished product,” says Lineo’s CEO Francois Vanfleteren. Lineo’s portfolio comprises FlaxPreg, FlaxPly and FlaxTape, introduced in the following examples by some interesting business cases. FlaxPreg With the help of FlaxPreg, a new method of combining the damping properties of flax with the well-known high performance of carbon fibre is being used to make bicycles which will dampen vibration and provide more comfort for the riders. The ultimate technical goal was to combine the damping properties of flax with the well-known high performance of carbon fibre without sacrificing mechanical performance. Using hybrid technology to combine flax fibres and carbon fibres, up to 25% of flax fibres have been used for different parts of bicycles with a flax/epoxy commercial prepreg (preimpregnated composite fibres), made from a unique yarn treatment and impregnation process, which overcomes past technology problems of working with flax. When optimally engineered, a carbon-flax structure can exhibit significantly higher damping behaviour than its full-carbon counterpart of equal weight. In addition to the increased damping the right use of flax layers simultaneously improves the buckling strength and stiffness of the composite part by up to 25%. Once more, this is due to the lower density of flax fibres. Thus, when replacing an intermediate carbon layer by a flax layer of equal weight, the distance between the remaining top and bottom carbon layers is increased, resulting in a carbonflax-carbon sandwich structure with higher stiffness than the full-carbon reference part. “Initially working with FlaxPreg was quite challenging, but the hurdles have been overcome, and now it is possible for new products to contain more FlaxPreg“, said Francois. Intrinsic flame resistance is another property which will be explored and will certainly make flax fibres attractive to other markets, such as transport. Major markets to benefit from the new eco-friendly technology are sports, leisure, furniture and transport, with cycling and tennis being the first sectors where the technology has been put into commercial production. FlaxPly FlaxPly is a family of semi-finished flax-fibre products available in (UD) unidirectional and balanced fabrics. The products are compliant with main thermoset resins on the market and are suitable for many applications in marine 18 bioplastics MAGAZINE [04/14] Vol. 9
Biocomposites or architectural markets. FlaxPly can be used with all wet processes such as infusion, hand lay-up, RTM, VARTM, etc. Lineo supplied FlaxPly reinforcements for the first ever racing boat prototype to incorporate up to 50% of natural flax fibre in the composite structure. The boat, which has been called the Araldite takes its name from Huntsman’s award winning Araldite ® range of products. It is a 6.5m long and 3m wide, ergonomic, lightweight Mini Transat racing boat prototype – the smallest offshore racing boat allowed to cross the Atlantic. Designed by Regis Garcia to showcase the possibilities of incorporating flax fibres into the composite structure of an open sea sailing prototype, the boat was built at the wellknown IDB Marine de Tregunc shipyard in Brittany, France. With acceptance and funding received from C.I.P.A.LIN, the French Interprofessional Committee for the Agricultural Production of Flax, the project has been completed in just over 12 months. FlaxTape FlaxTape is the best flax reinforcement on the market, in terms of performance and price. The cost of yarn production is prohibitive. The manufacture of a yarn involves several processing steps. For example, the production of a conventional flax yarn usually requires scutching, hackling, four to six passes of drawing and the final spinning operations. The cost of the final spinning operation alone typically accounts about half of the total cost of the whole fibre-to-yarn process. The weaving of yarns into a fabric is another labour-intensive and costly process, involving warp preparation, threading, weft preparation and weaving. Significant cost savings can be realized if a highly aligned reinforcement structure can be produced without involving the expensive spinning and weaving operation. Lineo worked to find processes for converting fibres directly into a unidirectional non-woven tape that can compete with unidirectional yarns and woven fabrics in final composite mechanical performance. The result is FlaxTape, a tape of unidirectional natural flax fibres that offers a number of advantages because it is produced without involving any spinning and weaving operations: FlaxTape doesn’t need treatment to improve wettability because its wettability is already very good. The flat product needs less resin than other traditional products. In comparison to flax fabric, which cannot be produced lighter than 150 g/m², FlaxTape Lineo can produce very light reinforcements down to 50 g/m². “With the FlaxPly and the FlaxPreg, we showed that flax fibre reinforcements have a real interest in the world of composites. But compared to glass fibre reinforcements flax fabrics are too expensive. To have a chance to gain other markets (like transport), it was necessary to go further, do better. And with the FlaxTape we succeeded!”, François Vanfleteren said. Application examples are musical instruments or sandwich panels for automotive applications [1]. MT [1]: Khalfallah, M. et.al.: Flax/Acrodur® sandwich panel: an innovative eco-material for automotive applications; jec composites magazine / No89 May 2014 www.lineo.eu bioplastics MAGAZINE [04/14] Vol. 9 19
