Influence of rapid high-temperature processing on the interface of CF/PEEK, a quick and effective method for enhancing the IFSS

This study explores the effect of rapid high-temperature processing on the interface of carbon fibre (CF) reinforced poly-ether-ether-ketone (PEEK). Specimens that have been thermally treated at slower and faster heating rates and specimens that have not been post-manufacturing treated (virgin) are examined with single fibre pull-out tests. A comparison between their interfacial shear strength (IFSS) and their failure modes takes place. Scanning electron microscopy is used to assess the surface morphology of the thermally treated specimens, and partly cross-polarised microscopy is employed to investigate the development of transcrystallinity. Furthermore, to identify the extent of thermal degradation the specimens are examined with attenuated total reflection Fourier transform infrared spectroscopy. At faster heating rates, an improved interfacial adhesion up to 25% is found at temperatures where a low-level thermal damage is induced. At higher temperatures and despite the increased thermal damage, an IFSS increase of up to 10% is still identified. This is due to the beneficial formation of thermal residual stresses upon rapid high-temperature processing and shows that these processing conditions could effectively serve for enhancing the interfacial adhesion of CF/PEEK.