Fracture Mode Transition in Unidirectional CFRP

Longitudinal tensile tests were conducted on necked-on-thickness specimens to clarify the factors affecting fracture mode transition in unidirectional CFRP. Specimens having fiber volume fraction ranging from 30% to 70% were tested in the range of environment temperature from room temperature (23°C) to -150°C, and the fracture morphologies of each specimen were examined. The results revealed that a transition of the fracture mode from interlaminar shear fracture to tensile fracture occurred when the thickness of the necked region (t), fiber volume fraction (Vf) and testing temperature decreased. This transition is due to the change in the relationship between tensile fracture load, P_σ^∗, and interlaminar shear fracture load, P_T^∗. The tensile fracture mode is more likely to occur at low values of Vf, small t and low testing temperature. A three-dimensional fracture mode map showing the effects of these three factors on fracture mode is presented.