Tribological performance of PEEK based hybrid composites reinforced with short carbon fibers and nano-silica

In this study, the tribological performances of poly-ether-ether-keton (PEEK) hybrid composites reinforced with short carbon fibers (SCF) (20 vol%) and surface modified nano-SiO2 particles (1, 1.5 and 2 wt%) were examined. Composites were fabricated by melt-mixing process at 400 °C. The polymer was in granulated shape, the original length of fibers was 6 mm and the size of nano-SiO2 particles was 13 nm. Micro-hardness tests were performed and presented a significant increase in hardness of the composites due to the presence of SCFs and nano-SiO2 particles. The effects of nano-SiO2 content on tribological properties of PEEK/SCF/nano-SiO2 composites were investigated. Tribological tests were carried out in 2, 3.75, 6.25 and 10 MPa normal pressures using pin-on-disk configuration. All of the tests were performed at room temperature in dry sliding condition at sliding velocity of 0.25 m/s. In order to investigate the wear mechanisms involved in different tribological conditions, worn surfaces were examined using scanning electron microscopy (SEM). Under all applied pressures, incorporation of nano-SiO2 particles remarkably reduced the friction coefficients. Also increasing the nanoparticles content led to decrease in friction coefficients in nearly all conditions. However, in terms of the enhancement in wear resistance of the composites, there was a strong dependence on the applied pressure.