Abstract: This study investigates the flexural mechanical properties of repaired composite foam sandwich structures with non-penetrating damage. Mechanical performance tests were conducted on composite panels and foam cores, and a high-fidelity finite element analysis model for sandwich structures was established incorporating the 3D Hashin failure criterion, Crushable Foam plasticity model, and B-K adhesive failure criterion. Four-point bending performance tests were performed on repaired structures with non-penetrating damage. The damage evolution and failure mechanisms of the repaired structures under bending loads were systematically investigated through the integration of finite element analysis and experimental results. Parameter optimization of additional repair plies was accomplished based on the high-precision finite element model. The results indicate that the proposed model integrating three failure criteria for laminates, foam cores, and adhesive layers demonstrates high computational accuracy, with deviations of 4.15% in flexural strength and 2.07% in flexural stiffness compared to experimental averages. Both finite element analysis and experimental verification effectively reveal the damage propagation path and failure modes of repaired structures under bending loads. The optimized repair scheme achieved 90.68% strength recovery rate, demonstrating significant engineering applicability.

Key words: foam sandwich structure, four-point bending, finite element analysis, progressive damage analysis, adhesive repair, composites