Experimental analysis of mechanical properties of composites reinforced by flax and basalt fibres

Even if the “fully green material” is far away from existing, a growing number of green advancements exist in composite technologies, which are able to reduce the negative impact on people or environment. Numerous research groups are, for instance, dedicated to minimising the environmental impact of polymer composite production using polymer matrices derived from renewable resources such as polylactide (PLA), thermoplasticstarch (TPS) or thermoset matrices. Their high renewable content derives from vegetable sources and, combined with natural reinforced fibers (NF) to form environmentally friendly and fully degradable composite laminates. In this way, these matrices represent a potential substitute for petroleum based ones. Natural matrices are therefore partially or totally obtained by renewable sources and/or made by biodegradable polymers. The availability of ecobased polymer matrices is nowadays still relatively scarce, but it rapidly grows as more studies are performed and more information is obtained. The employment of these bio-based polymers depends on the possibility to modify their properties in order to ease their processing, at the same time improving the toughness of the final biocomposite. On the other hand, natural reinforcements are now widely known and quite largely used. Natural fibers are compounds combining cellulose, hemicellulose and lignin. They can be derived from leaf (e.g. sisal), bast (e.g. flax, hemp), seed (e.g. cotton) and fruit (e.g. coir). They are biodegradable and “carbon positive” since they absorb more carbon dioxide than they produce.They are non-irritating and tend to be non-abrasive, reducing wear on tools during manufacturing. Natural fibers have lower density values: in substitution of synthetic ones, they reduce the weight of an artifact by up to 40%, perfectly fitting non structural uses. It is even possible to improve flexural strength, stiffness and ductility of materials. In contrast, natural fibers provide composites with not excellent and largely variable mechanical proprieties, limiting therefore their use in structural applications.