Fatigue behavior of continuous carbon fibre reinforced polyetheretherketone composite material, CF/PEEK is investigated. Tests are performed for three kinds of specimen types; namely parallel-sided coupon type, width waisted type and dog bone type specimens, to determine an appropriate specimen configuration for fatigue testing of CF/PEEK material. Tests are also performed for a thermosetting composite material Graphite/Epoxy for comparison. Multi-angle lay-ups employed are quasi-isotropic ones, namely, $[-45/0/45/90]_s$ for CF/PEEK and $[-45/90/45/0]_s$ for Graphite/Epoxy. Variation of stiffness with fatigue cycling is measured by unloading elastic compliance method using a pesonal computer system.
The test results show that the CF/PEEK material is very sensitive to stress concentration and consequently, the width waisted type specimen is most appropriate for fatigue testing of this material. While the degradation of stiffness of thermosetting composite material Graphite/Epoxy is relatively large, with fatigue cycling, thermoplastic composite material CF/PEEK shows little variation of stiffness throughout fatigue life.
