Effect of SCF Content on Mechanical and Tribological Properties of PEEK Composites

In this study, compression-molded SCF/PEEK composites with fiber contents ranging from 0 to 20 wt% were prepared, and the effects of fiber content on microstructure, mechanical properties, fracture behavior, and tribological performance were systematically investigated. The results show a pronounced non-monotonic dependence of performance on SCF content. The composite containing 10 wt% SCF exhibits the best overall performance, with tensile strength, flexural strength, and fracture toughness of 124 MPa, 205 MPa, and 17.5 MPa·m^1/2, respectively. Meanwhile, the steady-state friction coefficient decreases to approximately 0.05, and the wear rate is reduced to 8.1 × 10⁻¹⁴ m³/(N·m). SEM observations reveal that uniform fiber dispersion and continuous fiber-matrix interfaces are achieved at this fiber content. In situ tensile scanning electron microscopy directly reveals interfacial microcracking, crack deflection, fiber bridging, and fiber pull-out during deformation. Worn surface analyses further demonstrate that carbon fibers form a stable load-bearing framework during sliding, which effectively reduces direct contact between the polymer matrix and the counterface. These results provide experimental insight into the relationship between fiber content, damage evolution, and mechanical and tribological performance in compression-molded SCF/PEEK composites.