Tensile and compressive behaviour of multilayer flax-rib knitted preform reinforced epoxy composites

Abstract

Flax fibres can be considered as a natural composite, made of concentric layers in which cellulose microfibrils are surrounded helicoidally in a polysaccharidic matrix. They are characterised by low density, high aspect ratio and good specific mechanical properties. These considerations make flax a potential contender for reinforcement in polymer matrix composites, as replacement for the widely used glass fibres. 1×1 rib knitted structures are manufactured on a V-bed manual knitting machine using flax yarn. Composites with two and four rib knitted preform layers were fabricated in a hot press. Tensile and compressive tests were carried out and the failure mechanism was analysed, structure of the broken end of the composite was observed by scanning electron microscope (SEM). It is observed that tensile strength and stiffness is a product of the fibre/matrix synergy, whereas the compressive strength and stiffness are contributed by the reinforcing matrix.