Mechanical Properties of Needle Punched Chopped Strand Mat Composite with Open Hole

Mechanical joints are usually and easily used for joining structural parts. However, for joining composite parts, stress concentration at the edge of circular hole of composite laminates leads local and ultimate destruction of the entire structure. Therefore, needle punching techniques were focused on to improve composite strength around open holes. Needle punch process can make handling abilities of textile fabrics by special needles for entangling fibers. By applying this technique, interlaminar properties of the composite laminates can be improved, therefore restrain of crack propagation at open holes by needle punch technique can be expected. However, effect of needle punch process on tensile properties have not been investigated. In this study, effect of needle punch process for glass fiber chopped strand mat as a reinforcement of composite materials on tensile properties of the composites with an open hole was investigated by changing needle punch density. The tensile strength was increased and decreased with increase in needle punch density. From the crosssectional observation, dispersion of fibers by kneedle punch process was the reason to improve mechanical properties.