An evaluation of the effects of moisture content on the modulus of elasticity of a unidirectional flax fiber composite

Results of tensile tests on “wet” and “dry” flax yarn are presented and these show the large effect that moisture content (MC) has on flax fiber modulus of elasticity (MOE). These results are compared to others from tensile tests on flax fiber reinforced epoxy unidirectional composites (FFREUC) made from “wet” and “dry” fiber. The homogenized fiber MOEs have been estimated for the composites using the inverse rule of mixture. Fiber MOE appears better for dry fiber (by around 20%) for both the yarn and composite. It is proposed that this difference is the result of changes to the quality of adhesion between matrix and fiber. Adhesion would appear to be better for wet fibers.