Effect of heat treatment on carbon fiber surface properties and fibers/epoxy interfacial adhesion

Abstract

Carbon fiber surface properties are likely to change during the molding process of carbon fiber reinforced matrix composite, and these changes could affect the infiltration and adhesion between carbon fiber and resin. T300B fiber was heat treated referring to the curing process of high-performance carbon fiber reinforced epoxy matrix composites. By means of X-ray photoelectron spectroscopy (XPS), activated carbon atoms can be detected, which are defined as the carbon atoms conjunction with oxygen and nitrogen. Surface chemistry analysis shows that the content of activated carbon atoms on treated carbon fiber surface, especially those connect with the hydroxyl decreases with the increasing heat treatment temperature. Inverse gas chromatography (IGC) analysis reveals that the dispersive surface energy γ S d increases and the polar surface energy γ S sp decreases as the heat treatment temperature increases to 200. Contact angle between carbon fiber and epoxy E51 resin, which is studied by dynamic contact angle test (DCAT) increases with the increasing heat treatment temperature, indicating the worse wettability comparing with the untreated fiber. Moreover, micro-droplet test shows that the interfacial shear strength (IFSS) of the treated carbon fiber/epoxy is lower than that of the untreated T300B fiber which is attributed to the decrement of the content of reactive functional groups including hydrogen group and epoxy group.