Fatigue Behavior and Modeling for Thermoplastics

In this study, the cyclic behavior and the microstructure under cyclic loading of a semi-crystalline thermoplastic polyether ether ketone (PEEK) are investigated. Macroscopic strain life experiments under uniaxial loading condition were conducted at strain amplitudes ranging from 0.02 mm/mm to 0.04 mm/mm and at ambient temperature. Scanning electron microscopy (SEM) analysis was performed on fatigue specimens to examine crack incubation sites and microstructural inclusions responsible for incubating fatigue cracks. Other microstructural inclusion properties including inclusion type (pore or particle), inclusion size, and nearest neighbor distance of inclusions were also obtained. Based on the experimental results, the strain-based fatigue model was employed to obtain strain-life fatigue properties and z-N fatigue curves of PEEK.