Abstract: L-shaped laminates are the most common and critical composite components in commercial aircraft, and the study of their failure mechanism is very important for the safety of aircraft structures. The crack propagation in matrix and the delamination failure between plies are the two most important failure mechanisms of L-shaped composite laminates. These two failure mechanisms may occur simultaneously and have coupling effects. In this paper, two sets of numerical analysis models are presented to describe the failure process of L-shaped composite laminates. In Model Ⅰ, zero-thickness cohesive elements are inserted between plies in the curved region of L-shaped laminates to simulate delamination and radial-pattern zero-thickness cohesive elements are inserted in the 90° layer to simulate matrix cracks. In Model Ⅱ, the XFEM method was used to simulate the initiation and propagation of matrix cracks and the cohesive behavior method was used to simulate the delamination. In comparison with the experimental results, the feasibility of the proposed methods is validated. Furthermore, the capability as well as the advantages and disadvantages of the two models in terms of failure modes and critical load predictions are evaluated. The results show that both models can describe the propagation of matrix crack and delamination as well as possible coupling effects. The failure modes predicted by numerical analysis agree well with the experimental results, and the predicted initial failure loads and maximum failure loads are also in good agreement with the experimental results.

Key words: L-shaped laminate, intra-laminar cracking, delamination, XFEM, cohesive elements, composite