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For the damage proprieties of sandwich composite L-joint with stiffener under bending load, the Hashin failure criterion is used to predict the initial damage of L-joint, the principle of energy dissipation based on damage and material linear softening process is used to predict the stiffness degradation of L-joint, and the cohesive element based on traction and separation model is used to simulate damage of the interface layer. First, the finite element model (FEM) is established by Abaqus, whose rationality is verified by comparing the FEM results with the test results in other literature. Second, the influence of skin's thickness and chamfer radius at the intersection on the bending capacity is studied based on FEM. The results showed that increasing the chamfer radius is the best way to improve the joints' stiffness, and thickening the skin at the intersection is the best way to improve the bearing capacity of the joint.

The stiffness is the main reason that restricts the large-scale of composite ships, the basis to solve this problem is to solve the stiffness of composite ships’ skeleton structure. Based on classical laminates theory, this paper calculated the equivalent in-plane stiffness and bending stiffness of composite hat stiffened laminate using equivalent stiffness principle. The hat stiffened laminate can be simplified and equivalent to orthotropic laminates using this solution idea, which solves the problem that it is difficult to obtain the analytical solutions of deformation, stress and strain of stiffened laminate. The research results can be used to calculate the stiffness of composite stiffened laminate and the local or global stiffness of the hull girder with such a skeleton structure.