Tensile Properties of an Epoxy Resin Matrix Composite Reinforced with Needle-Punched Flax UD Fiber Bundles

Green composites have high specific strength and rigidity that are comparable to those of glass fiber reinforced plastics (GFRP) and other artificial fiber reinforced plastics. A recently developed unidirectional sheet of flax fibers is available as a laminate similarly to carbon fibers. Laminates generally have low strength in the thickness direction. Although Zanchor is often applied to overcome this shortcoming, Zanchor effects on the mechanical properties of green composites remain unclear. For this study, artificial entanglement was created by needle-punching of a unidirectional flax fiber sheet. Epoxy resin matrix composites were produced using hot-pressing to elucidate tensile property changes. Results show that needle-punching decreased the tensile strength and Young's modulus in the fiber direction, although these properties increased in the direction vertical to the fiber. Furthermore, by quantifying the out-of-plane fiber orientation, we assessed effects of two fiber-orientation changes deriving from needle-punching.