Enhanced interfacial properties of high-modulus carbon fiber composites via molecular assembly on fiber surface

To improve interfacial properties of high-modulus carbon fiber (HMCF) composites, a nanostructured interphase with multiple interaction is constructed by molecular assembly of naphthalene diimide (NDI) on HMCF surface. NDI can react with the matrix while being compatible with the graphite-like carbon fiber surface, which improves the interfacial adhesion. The surface physicochemical properties and surface energy of different HMCFs were investigated. The interfacial properties of HMCF composites were measured by interfacial shear strength (IFSS) test and transverse fiber bundle tensile (TFBT) test. A significant improvement of the IFSS for NDI assembled HMCF of 64 % compared to that of unsized HMCF was obtained, which were attributed to the release of stress concentration and crack propagation from HMCF surface toward the nanostructured interphase with multiple interaction. The schematic models of interphase reinforcing mechanisms were proposed accordingly.