Mixed mode II and III interlaminar fracture resistance of cross-ply carbon/epoxy composite laminates was experimentally and numerically evaluated using DNSCB (double notched split cantilever beam) test method, which enables a stable interface damage growth under the mixed-mode condition. Specimens with initial delaminations at two interfaces of 0° layers were used. The fracture morphology strongly depended on the mixed mode ratio. Complex damage comprising delaminations and inclined matrix cracks grew in the middle of the specimen where mode III component was dominant, while simple delaminations propagated outside the region of the complex damage where mode III component was comparatively small. Apparent dependence of the fracture toughness on the mixed-mode ratio was not found in the results obtained from the region of the simple delamination. The fracture resistance was considerably higher in complex damage region than in the region of simple delamination as expected from the significance of the damage state.
