Direct growth of thermally reduced graphene oxide on carbon fiber for enhanced mechanical strength

In this study, carbon fiber (CF) composites were prepared by synthesizing thermally reduced graphene oxide (TRGO) directly on the surface of CFs in order to reinforce the interface between the CFs and the matrix. The conformal and robust coating of TRGO on the CF surface is achieved by the direct conversion of shellac, a low-cost natural polymer, to TRGO via single-step low-temperature (400–700 °C) annealing. X-ray photoelectron spectroscopy, Raman analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, contact angle measurement, and energy dispersive spectrometry results confirmed the synthesis of high-quality TRGO, which prompted hydrogen bonding and mechanical interlocking at the composite interfaces. The CF-TRGO composites showed 60 and 152% higher interlaminar shear strength (ILSS) and flexural strength, respectively than the untreated CF composites. The fracture surface analysis by SEM further reveals that the interfacial bonding between the matrix and the CFs increased significantly with TRGO coating.