Tensile properties hybrid effect of unidirectional flax/carbon fiber hybrid reinforced polymer composites

Abstract

To improve the mechanical properties of flax fiber reinforced polymer composites, flax/carbon fiber hybrid reinforced polymer composites were prepared by wet winding. The effects of carbon fiber volume fraction, carbon fiber monolayer thickness, and hybrid mode (carbon fiber dispersion) on the properties of hybrid composites were studied by tensile tests considering existing theoretical models. The results showed that the minimum repeating unit of flax fiber as skin and carbon fiber as core can yield a positive hybrid effect. In addition, a lower carbon fiber volume fraction reduced the carbon fiber monolayer thickness, and a higher degree of dispersion emphasized the positive hybrid effect of the hybrid composite. The stress–strain curves of the composite did not exhibit pseudo-ductility given the negligible difference in failure strain and large difference in modulus, such that the carbon fiber layer could not fracture multiple times. In an optimized hybrid composite, introducing 26.4% carbon fiber increased the composite strength by 129.3% compared with the flax fiber reinforced polymer and the composite toughness by 32% compared with the carbon fiber reinforced polymer.