Mechanical Properties of Needle Punched Chopped Strand Mat Composites

Abstract

Fiber Reinforced Plastics (FRP) have been expected to be used for structural materials in various field because of its high specific stiffness and strength. In the case of using FRP for automotive structures, joint structure must be needed. Most comfortable and reliable joint system is mechanical joint with bolt and nut or rivet. However, mechanical joint system for FRP have a problem; mechanical properties of composite laminates decrease because of delamination around hole by stress concentration. Therefore, improvement of interlaminar strength is important. In this study, needle punching techniques were focused on to improve interlaminar strength of FRP around open holes. This technique are usually used for fabrication of non-woven fabrics. In needle punching process for non-woven fabrics, fiber webs are punched and entangled by lots of special needles (called felt needles) with many barbs set on the metal plate. By using felt needles, a part of fibers of reinforcement in in-plane direction can be aligned in out-of-plane direction. In this study, needle punch process was applied to chopped strand mat. Tensile test, bending test and end notched flexure test were carried out, and effect of needle punch density on tensile, bending and interlaminar fracture toughness properties on fracture mechanism of FRPs with needle punched chopped strand mat were investigated.