Uniaxial compression tests were carried out to investigate the mechanical properties of polyetheretherketone (PEEK) with different contents of short carbon fibers (CF).Results show that the mechanical strength of PEEK can be improved with a certain mass fraction of CF. In order to study the viscosity of PEEK, static creep tests were performed considering the effects of stress level and content of CF. It is found that CF enhances the creep resistance of PEEK and 20 wt% carbon fiber-reinforced PEEK has the best performance. Moreover, the creep strain of the composites increases with increasing stress level. Subsequently, the ratcheting experiments under uniaxial cyclic compression with the stress-controlled condition were conducted. It is shown that the ratcheting strain increases with increasing stress amplitude and the holding time of peak stress. However, the effects of stress rate and content of CF on ratcheting strain are opposite. Meanwhile, the dependence of ratcheting behavior on loading history was also investigated. The results show that ratcheting strain is significantly affected by loading history of stress amplitude due to cyclic hardening of the material, while the effect of loading history of stress rate on ratcheting strain is negligible. K E Y W O R D Scarbon fiber, creep property, femoral implant, polyetheretherketone, ratcheting behavior

Ultrahigh molecular weight polyethylene (UHMWPE) artificial joint has remained the preferred polymer component in total joint replacement surgery. However, more and more concerns have been raised about the failure of UHMWPE components due to the initiation and propagation of cracks at the notches with fixed functions. For this reason, biaxial fatigue crack growth (FCG) experiments of UHMWPE reinforced by carbon nanofibers (CNF) and hydroxyapatite (HA) were carried out using elastic–plastic fracture mechanics theory. The FCG resistance of UHMWPE, UHMWPE/CNF, and UHMWPE/HA was compared, and the effects of stress ratio (R) value and phase difference on FCG rate were investigated. At the same time, the influence of loading path was considered, and the corresponding crack path was analyzed. Results suggest that UHMWPE/CNF has better FCG resistance and the FCG rate increases with the increase of R value and the existence of 180° phase difference. In addition, crack bifurcation behavior is not observed under nonproportional loading conditions. The findings in this study will provide experimental validation and data support for better clinical application of UHMWPE‐modified materials.

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