An R-curve effect-included delamination growth criterion for mixed-mode I/II delamination predictions of composite laminates

Most existing mixed-mode I/II delamination growth criteria are purely empirical or semi-empirical fitting functions of the experimental fracture toughness, which limit their wide range applications. In this work, a novel delamination growth criterion is proposed for mixed-mode I/II delamination predictions considering the significant R-curve effects in composite laminates. Its adequacy and accuracy are validated by the available experimental data for two different composite materials from literature. Both the trend and the magnitude of the predicted failure loci show fairly good agreements with the experimental ones. Only two experimentally obtained parameters, i.e. the pure mode I and mode II fracture toughness curves are required in the proposed criterion, which makes the proposed criterion easy to use. The proposed criterion can be applied for the evaluation of the mixed-mode I/II delamination growth behavior and thus the prediction of the structural strength, which may have important theoretical significance and engineering guidance value for the damage-tolerant design of composite materials and structures.