The optimisation of flax fibre yarns for the development of high-performance natural fibre composites

Abstract

Currently most developments in the area of natural fibre reinforced composites have focused on random discontinuous fibre composite systems. The development of continuous fibre reinforced composites is, however, essential for manufacturing materials, which can be used in load-bearing/structural applications. The main problem in this case is the optimisation of the yarn to be used to manufacture the textile reinforcement. Low twisted yarns display a very low strength when tested dry in air and therefore they can not be used in processes such as pultrusion or textile manufacturing routes. On the other hand, by increasing the level of twist, a degradation of the mechanical properties is observed in impregnated yarns (e.g. unidirectional composites) similar to off-axis composites. Additionally, a high level of twist decreases the permeability of the yarns. This problem is addressed in the current work using yarns based on both long and short flax fibres.