Effects of Carbon Fiber Length and Orientation on the Tribological Properties of Polyetheretherketone Based Composites

In order to prepare polyetheretherketone (PEEK) based self-lubricating materials, carbon fiber (CF) filled PEEK/polytetrafluoroethylene (PTFE) composites were prepared by melt extrusion and injection molding. The effects of CF contents, length and orientation in matrix on the tribological properties of composites were investigated. The surface morphologies of wear scar were observed on scanning electron microscope, so as to explore the tribological mechanism. The effects of fiber orientations in matrix on the tribological properties of composites were also investigated using 10% CF filled composites. The results showed that the average friction coefficient and wear rate of the composites decreased initially and then increased with the increase of CF contents. It is also found that the average friction coefficient of longer CF (L-CF) filled composites was lower than that with shorter CF (S-CF) obviously when CF addition was above 10%. Compared with the sliding in other directions, the sliding in X direction (melt flow direction), or the CF arrangement direction, had relatively lower average friction coefficient, but higher volume wear rate. The sliding in Y direction (vertical direction of X) had higher average friction coefficient and lower wear rate than those in X direction. The origination of the differences was discussed, and the tribological mechanism was proposed.