Effect of Needle Punch Treatment on Strength Properties of a Flax FiberReinforced Composite

Green composites have been attracting attention as an alternative material of artificial fiberreinforced materials such as GFRP (glass fiber-reinforced plastics). According to our past studies, we compounded flax sliver and poly-lactic acid resin (PLA), one of biodegradable resins, and developed a flax fiberreinforced green composites as an environment-friendly material. In addition, the mechanical properties of this material were clarified through a tensile test. In this study, a composite materials was prepared by hot-press method using needle-punched flax sliver, and the effect of the number of needle-punch on the tensile properties was investigated. Results show that the fiber volume fraction tends to decrease through needle punching process. Results also show that tensile strength of the composites along the fiber direction decreases by needle-punch, but in the case of 400 times repeatedly needle-punched sliver, the composite strength increases higher than the composite reinforced with as-supplied sliver, if the strength level is converted into the fiber stress level at the composite break. On the other hand, the composites' strength along the transverse fiber direction decreased less than the strength level of neat PLA.