Tension-tension fatigue behavior of hydroxyapatite reinforced polyetheretherketone composites

Hydroxyapatite (HA) particle reinforced polyetheretherketone (PEEK) composites with 5, 10, 20, 30, and 40% (by volume) HA content were subjected to tension-tension fatigue under load-controlled mode. Results of quasi-static tensile tests indicated that the tensile stiffness of the HA/PEEK composites increases while their tensile strength decreases, with an increase in HA content, up to 40% (by volume). Stress-life (SN) and stiffness degradation data were obtained. The fact that all of the specimens survived cyclic load at 50% ultimate tensile strength (and below) and the high estimated fatigue strength at 1 million cycles suggest that HA/PEEK composite is a promising fatigue-resistant material for biomedical applications. Microscopic examination of cyclically loaded specimens revealed evidence of interfacial failure between the filler and the PEEK matrix, and subsequent initiation and propagation of micro cracks in the matrix that cause fatigue failure.