Effects of the air oxidation of carbon fibers on the properties of 3D braided carbon/resin composites

A three-dimensionally braided carbon fiber reinforced carbon/epoxy resin (C/Ep) composite was prepared by vacuum impregnation, and the effect of air oxidation of the fibers on the properties of the composite were investigated by SEM, nitrogen adsorption and mechanical testing. Results show that the specific surface area and surface roughness of the oxidized carbon fibers increase while their tensile strength decreases with increasing oxidation temperature or time. The flexural strength, flexural modulus, and shear strength of the C/Ep composites under the optimum treatment at 450℃ for 1h were increased by 149%, 91% and 29% respectively compared with the untreated samples, but the impact strength was decreased by 23%.