Delamination resistance of Fiberite's IM7/977-1 carbon fibre/epoxy composite was evaluated under Mode I, mixed Mode I/Mode II in the ratio of 4/3, and Mode II loadings. The need for Mode I pre-cracking of the UD composite beam prior to the actual fracture test was demonstrated. The fracture toughness data were found to fit a simple power law failure criterion and a physical meaning for the fitting parameter was suggested. Fractographic studies were carried out by SEM examination near the crack initiation areas of the fracture samples and illustrated the gradual change in the micromechanisms of failure as the loading mode changed from crack opening to forward shear.
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