Flexural Properties of Unidirectional Composites Laminarily Reinforced with Mesophase Pitch Based Carbon Fibers and Alumina Fibers.

Abstract

Unidirectional multistack composites of two kinds of composite prepregs, mesophase pitch-based carbon fibers (MCF)/epoxy and alumina fibers (ALF)/epoxy, were prepared. Since MCF has higher modulus and smaller tensile elongation than polyacrylonitrile-based carbon fiber (PCF), the flexural strength and modulus of the multistack composites were found to be different from the similar composites prepared by combination of PCF and ALF. In the interply-type MCF/ALF multistack composites which have the AFL perpregs in the center, fracture began in the top layer (compression side) with the bending load decreasing. In the composites having MCF prepregs in the center, small cracks were formed in the MCF layer with a slight yielding of the bending load. Since the fracture was slowed down and even stopped by the hybrid lamination, abrupt destruction of the whole composite was successfully suppressed. The modulus of the composites, which could be elucidated by the lamination beam theory, increased with increasing number of MCF layers and was much higher than that of PCF/ALF multistack composites.