Comparison of fracture toughness (GIC) values of polyetherimide (PEI) and a carbon-fibre/PEI composite: an experimental and theoretical study

GIC values are measured for polyetherimide (PEI) under quasi-static and low speed impact conditions. A novel technique is used to obtain the quasi-static GIC value, based on video-recording of crack growth under test in a single specimen. Further measurements of GIC for a carbon fibre/PEI composite are made, which show greatly reduced fracture toughness of the composite compared to the matrix alone. Causes of the lowered efficiency of translation of the matrix toughness into the composite are explored, using FEA modelling to examine the effects of matrix/fibre interface strength and resin-rich layers on the stress fields in the vicinity of the crack tip