Improving Surface Property of Carbon Nanotube Grown Carbon Fiber by Oxidization Post-treatment

Oxidization treatment has been successfully applied on carbon nanotubes grown carbon fiber (CNTs-CF) to improve the surface activity and the interfacial property of CNTs-CF/epoxy resin (CNTs-CF/EP) composite. The surface element, morphology, and mechanical property of CNTs-CF have been systematically studied by X-ray photoelectron spectrum (XPS), scanning electron microscope (SEM), and single fiber tensile strength tester, respectively. The results indicate that the oxygen content on the CNTs-CF surface has been markedly increased from 2.5% to 19.4% after oxidization treatment, while the tensile strength shows no significant decrease. The CNTs layer on the surface protected the carbon fiber from corrosive oxidization agent, at the cost of collapsing and falling off of itself. Contact angle measurement and shear strength test have been introduced to investigate the interfacial property of CNTs-CF/EP composite. The result shows that the contact angle of resin to fiber has been reduced from similar to 39 degrees to similar to 35 degrees after oxidization, while the interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) has been improved by 14.32% and 12.4% compared with untreated CNTs-CF/EP, respectively. A model is proposed to explain the wave-shaped fracture surface phenomenon of the composite. This work could reveal a novel approach to further improve the surface property of carbon fiber after growing carbon nanotubes.