Correlation between properties of carbon fibers and interfacial fracture energy of carbon fiber/epoxy resin

By using the single fiber fragmentation test (SFFT) based on Wagner-Nairn-Detassis (WND) energy model, the interfacial fracture energy of five kinds of homemade and two kinds of foreign carbon fibers/epoxy resin systems for aeronautical structures was measured. The surface physical and chemical characteristics of the seven carbon fibers were analyzed by means of SEM, AFM, IR and XPS. Moreover, the correlation between the characteristics of carbon fibers and the interfacial fracture energy was studied. The results indicate that the interfacial fracture energy decreases due to the removal of the sizing agent on the carbon fiber surfaces, which means that the sizing agent may improve the interface toughness to some extent. Furthermore, within the laboratory experiments, the obtained results of the interfacial fracture energy are higher with the higher tensile strength and surface roughness of carbon fibers, which demonstrates the tensile strength and surface roughness have significant influences on the interfacial toughness. Comparing with these two factors, the type of sizing agent has a relatively small effect. The results have instructive significance for the studies of homemade high performance carbon fibers and the matching of carbon fiber/epoxy resin.