Material propertiesNanoindentation and nanoscratching responses of PEEK based hybrid composites reinforced with short carbon fibers and nano-silica

The micromechanical properties of PEEK based hybrid composites reinforced with short carbon fibers (SCF) and nano-SiO2 particles were examined using nanoindentation and nanoscratching methods. The composites were fabricated by the melt-mixing process at 400 °C. The neat polymer was in granulated form, the size of the nanoparticles was 13 nm and the original length of short carbon fibers was 6 mm. More than 30 nanoindentation and 3 nanoscratching tests were performed on each specimen. Surface topography of the indented and scratched regions was evaluated using AFM. The effects of reinforcing particulates on the typical nanoindentation load-displacement curves of the composites were investigated. Also, the overall reinforcing effects of the carbon fibers and nanoparticles were investigated. Nanoscratching tests were effectively performed to evaluate the frictional properties in the matrix, fiber and interphase regions and also to estimate the thickness of the interphase. There were notable differences between the nanoindentation responses and the microfrictional properties of the composites in matrix and fiber phases. Results showed a significant increase in hardness and elastic modulus due to the presence of reinforcing agents.