Effect of Preheat Treatment on Carbon Fiber Surface Properties and Fiber/PEEK Interfacial Behavior

In this work, the effect of preheat treatment on surface properties of carbon fiber (CF) and interfacial properties of CF-reinforced polyether ether ketone (CF/PEEK) composites was investigated in detail. The sized T700SC CFs were preheated based on practical thermoplastic composites processing conditions. The obvious mass loss was obtained due to the sizing agent degradation. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy demonstrated that the concentration of sizing agents and activated carbon atoms decreased apparently for preheated fibers. Pre-heat treatment had negligible effect on tensile strength. Transcrystallinity structures were observed at fiber/PEEK interfaces using polarizing microscope and they had similar transcrystallinity density before and after preheat treatment. The microbond test was performed to determine interfacial shear strength (IFSS) between fibers and PEEK matrix. The IFSS increased from 40.16 to 46.32 MPa by 15.34%, which was against the trend of activated carbon atoms. Furthermore, the mechanisms of interfacial adhesion enhancement were discussed. The sizing layer became weak interface region because of poor chemical bonding between sizing agents and PEEK. Removing sizing via preheat treatment could enhance the interfacial adhesion. (C) 2018 Society of Plastics Engineers