Influence of matrix ductility on the high-temperature fatigue behaviour of quasi-isotropic woven-ply thermoplastic and thermoset laminates

The tension–tension fatigue behaviours of quasi-isotropic woven-ply thermoplastic (Polyphenylene Sulphide – PPS) and thermosetting (Epoxy)-based laminates are discussed in this paper. The service temperature of these materials is such that Tg|C/PPS < T < Tg|Epoxy, and matrix ductility is expected to reflect on the fatigue behaviour. The contribution to the knowledge base from this work rests on the experimental evidence supported by microscopic evaluation at different stages of the fatigue life and fracture surface analysis. These observations exhibit two distinct damage accumulation scenarios in both laminates dominated by fibre breakage in carbon/PPS and debonding, as well as delamination in carbon/epoxy. The potential benefit of matrix-rich regions in woven-fabric laminates is the development of plastic yield zones at the cracks tip as intra- and inter-ply cracks propagate. Depending on matrix ductility, the localized matrix plasticization is instrumental in ruling fatigue damage mechanism, as it may delay the cracks onset and subsequent propagation.