Effects of Carbon Fiber Treatment on Interfacial Properties of Advanced Thermoplastic Composites

The surface free energy and composition of carbon fibers showed strong correlation with treatment history. In this report, untreated AU, surface-treated AS, and heat-treated (under vacuum) ASH carbon fibers were used in poly(ether ether ketone) (PEEK) and poly(ether sulphone) (PES) composite systems. The relationships between treatment of carbon fibers (thus surface characteristics of carbon fibers) and interfacial properties of advanced thermoplastic composites were investigated. Both single-fiber-composite samples and prepreg-made composite laminates were used. The interfacial shear strength was doubled in PEEK matrix and increased 16% in PES matrix, as revealed by single-fiber-composite. PES composite laminates showed improvement of 20% and 26% in TFS and SBSS, respectively, when changed from AU to AS fiber systems. The heat treatment reduced the surface free energy of carbon fiber by removing these functional group elements and reduced adhesion. In addition, the effects of carbon fiber surface composition are discussed.