Quasi-static and ratcheting properties of PEEK reinforced by carbon fibers under uniaxial and cyclic compression

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.