Irradiation and annealing effects on delamination toughness in carbon/epoxy composite

Gamma irradiation to various doses (4.8–27.2 MGy) was performed on unidirectional carbon fiber/epoxy resin composite plates. Unidirectional composite coupons irradiated to various doses were annealed at 180 and 250 °C, in vacuum. The strain energy release rate GIC, as a measure of delamination fracture toughness, was determined by Mode I fracture testing on double cantilever beam coupons. The glass transition temperature (Tg) of the tested coupons matrices was determined in DMA tests. The effects of irradiation and annealing on GIC values – the mean values of 10 propagation points (GIC,mean) and that of fracture initiation (GIC,init) – were established. These values were analyzed as a function of irradiation dose and annealing temperatures, having in mind glass transition temperature values changes, as well as the possible mechanisms and phenomena of irradiation and annealing.