Combined effect of moisture and test temperature on the pseudo-ductility of thin-ply carbon/epoxy-glass/epoxy hybrid composites

Two different glass/carbon fibre-epoxy interlayer hybrid composite specimen types (with continuous or discontinuous carbon layer) were investigated. Unconditioned and conditioned composite specimens were tested at various temperatures in order to study the temperature dependency and moisture sensitivity of the tensile and interlaminar properties of the hybrid composites. The tensile response of the unconditioned continuous specimens was barely influenced by temperature and the specimens failed in pseudo-ductile mode. The unconditioned discontinuous specimens delaminated stably at the glass/carbon interface. Increasing the test temperature from −50 °C to 80 °C, the mode II fracture toughness of glass/carbon hybrid composites decreased significantly. The effect of moisture significantly changed the behaviour of both type hybrid composites at all temperatures leading to unstable delamination and glass fibre failure as well. The main reason for this was the decrease in strength of the S-glass/epoxy layers.