Study of the Mode I and Mode II interlaminar behaviour of a carbon fabric reinforced thermoplastic

Delamination or interlaminar failure is a critical failure mechanism for fibre-reinforced composites and, therefore, has already been studied extensively by many researchers. However, it remains an active research topic, since every day new polymers with better mechanical properties are being developed for fibre reinforced composites. This manuscript describes an experimental study of both the Mode I and Mode II interlaminar behaviour of a 5-harness satin weave carbon fabric reinforced polyphenylene sulphide (PPS). The mode I crack growth was studied using the Double Cantilever Beam (DCB) setup, whereas the mode II behaviour was studied by the End Notch Flexure (ENF) test. For mode I, an unstable crack-growth was seen resulting in a saw-tooth like force-displacement curve. Therefore, a model based on Linear Elastic Fracture Mechanics was considered to determine GIC for both initiation and propagation. Furthermore, the effect of possible fibre-bridging was assessed and an online microscopic study was conducted so that the origin of the specific jumps in crack growth could be determined. For mode II, stable crack propagation occurred and the Compliance-Based Beam Method was used to determine GIIC for both initiation and propagation. It could be concluded that the considered approach worked well for this material and reproducible results and values were found.