Compressive and flexural performance and failure mechanisms of scarf-repaired marine PVC foam sandwich structures with through-thickness damage

Abstract

Marine composite foam-core sandwich structures are prone to full through-thickness damage under low-velocity impacts during service, which severely degrades their load-bearing capacity and operational safety. This paper presents a combined experimental and numerical study on the compressive and flexural mechanical properties of scarf-repaired PVC foam sandwich panels. A refined finite element (FE) model was established, integrating continuum shell elements with a progressive damage model for composite laminates, zero-thickness cohesive elements for adhesive interfaces, and a crushable foam constitutive model for the PVC core. Axial compression tests were carried out to validate the FE model, and the results show that the prediction error of the model for the ultimate load-bearing capacity is only 7.1%. The damage evolution laws and load transfer mechanisms under axial compression and four-point bending conditions were systematically compared and analyzed. The results indicate that axial compression failure is dominated by sudden global debonding and overall warping of the repair patch, exhibiting brittle characteristics; while flexural failure presents progressive layered characteristics, with damage concentrated at the adhesive interface and the patch crushing zone near the loading end. This study can provide a theoretical basis and engineering reference for the repair design of marine composite sandwich structures.