Enhanced interfacial property of carbon fiber reinforced epoxy composite based on carbon fiber treated by supercritical water/nitrate system

Abstract

Carbon fibers were surface treated with supercritical water/nitrate system to improve the interfacial adhesion of the carbon fiber/epoxy composite. The surface chemistry analysis showed that oxygen functional groups on the surface of the carbon fibers increased after treatment, which were mainly carbonyl and carboxyl groups. The surface microstructure observation indicated that the treatment obviously increased the surface roughness of the carbon fibers. Surface energy of the treated carbon fibers also increased. The increased functional groups, surface roughness and surface energy were beneficial to enhance the interfacial adhesion of the carbon fiber/epoxy composite. Compared with the untreated carbon fibers, the strength loss of the treated carbon fibers was less than 3% and the other mechanical properties were almost unchanged. The caclulated interfacial fracture energy and the interfacial shear strength of the treated carbon fiber/epoxy composite were enhanced by 19% and 29%, respectively, compared with the untreated carbon fiber/epoxy composite. In summary, supercritical water/nitrate treatment is a potential method for changing the inert surface of carbon fibers to improve the interfacial adhesion between carbon fibers and matrix.