Orientation‐Dependent Tribological Behavior of Carbon Fiber‐Reinforced Polyetheretherketone Composites Containing Carbon Nanotubes

Oriented carbon fiber (CF)/carbon nanotube (CNT)/polyetheretherketone (PEEK) composites were prepared using polyethyleneimine‐modified CF. The CF content was fixed at 10 wt%, while CNT contents of 0, 0.5, and 1 wt% were employed. Reciprocating dry‐sliding tests were conducted parallel and perpendicular to the CF alignment, and the worn surfaces and wear tracks were characterized by scanning electron microscopy and white‐light interferometry. Both the average friction coefficient and specific wear rate first decreased and then increased with increasing CNT content, and the composite containing 0.5 wt% CNT showed the best overall tribological performance. Its friction coefficient decreased from 0.093 to 0.082 under perpendicular sliding and from 0.096 to 0.090 under parallel sliding compared with the CNT‐free composite. Pronounced anisotropy was observed: perpendicular sliding produced a lower friction coefficient but a higher specific wear rate than parallel sliding. During parallel sliding, continuous plastically deformed PEEK contact plateaus promoted sustained adhesive shearing, while the aligned CF framework constrained matrix removal. During perpendicular sliding, transverse fibers interrupted the adhesive contact paths but caused periodic load redistribution and preferential wear of the PEEK matrix. Thus, friction coefficient and specific wear rate exhibited different orientation‐dependent trends.