Digital Image Correlation Analysis of Fatigue Degradation of Layered Polymer Composites (Polyetheretherketone/Polyetherimide, PEEK/PEI) with Carbon-Fiber Fabric Prepreg

Abstract— In this work, the relationship was considered between the structure and cyclic loading resistance of a layered composite consisting of PEI (PEEK) plate/PEI (PEEK) film/PEI-impregnated carbon-fiber fabric prepreg/PEI (PEEK) film/PEI (PEEK) plate by analyzing the time variation in the parameters of mechanical hysteresis loops calculated using digital image correlation. It was shown that the polyetherimide-based layered composite has low fatigue life under cyclic loading (0.8 of the yield strength), resulting from incompatible deformation between the PEI plates and the prepreg due to a layer interface formed by low-melting TecaPEI film. In the PEEK layered composite, the layer interface was formed by neat PEEK energy director and therefore had a little amount of defects, due to which the load was well transferred from the PEEK plates to the middle reinforcement layer. As a result, the fatigue life at a load level of 0.8 of the yield strength corresponded to high-cycle fatigue (more than 86000 cycles).