Tribological Coupling of Submicron‐Sized Particles With Carbon Fibers Containing Varying Surface Sizing Contents in PEEK Composites

ABSTRACT Short carbon fiber (SCF) reinforced polyetheretherketone (PEEK) composites incorporating graphite and submicron‐sized ZnS/TiO ₂ particles were fabricated to investigate the influence of carbon fiber surface sizing on tribological performance. Dry sliding tests were performed using a block‐on‐ring configuration over a wide range of normal pressures and sliding speeds. The results indicate that the tribological behavior of the PEEK composites is more sensitive to sliding speed than to normal pressure. Compared with neat PEEK, the introduction of SCFs combined with graphite and ZnS/TiO ₂ particles significantly reduces both the friction coefficient and wear rate. Notably, PEEK‐C reinforced with higher sizing content carbon fibers exhibited a 67% reduction in the friction coefficient and a 65% decrease in specific wear rate compared to PEEK‐B at 1 MPa and 4 m/s. Even under high loading of 4 MPa at 2 m/s, PEEK‐C maintained a 51% lower specific wear rate than PEEK‐B, demonstrating superior stability across a broad pv‐range. Microstructural analysis reveals that the enhanced wear resistance is mainly attributed to improved fiber‐matrix interfacial bonding and more efficient load transfer. In addition, optimized surface sizing promotes the formation of a continuous transfer film on the steel counterface, acting synergistically with ZnS/TiO ₂ particles to mitigate wear. These findings underline the critical importance of surface sizing in tailoring the tribological performance of SCF‐reinforced PEEK composites for demanding engineering applications.