Abstract: To address the issue of excessively high computational costs associated with 3D refined modeling in the ultimate strength analysis of large and medium-sized marine sandwich composite structures, an efficient “shell-solid coupling” simplified finite element model was proposed and validated. The 3D progressive damage failure criteria were dimensionally reduced and adapted to 2D shell elements. Taking a typical L-shaped stiffener connection structure as the research object, two simplified modeling strategies were comparatively evaluated: the coupling of solid elements for the core and shell elements for the skin (Method 1), and the equivalent overall shell element modeling for the entire sandwich panel (Method 2). The results indicated that Method 2 yielded significant deviations in predicting the basic structural stiffness. In contrast, Method 1, combined with a meshing strategy that allocates no less than 6 elements in critical regions (such as hat-shaped stiffeners), achieved a nearly hundredfold increase in computational efficiency while accurately reproducing nonlinear failure modes and keeping the ultimate load prediction error within 7%.

Key words: sandwich composite, braided composite, ultimate strength, progressive failure