Study on low-velocity impact response and residual strength of scarf-repaired foam-filled lattice composite sandwich panels

To ensure the structural integrity and safety of composite materials, effective repair methods are essential, particularly for foam-filled lattice composite sandwich panels (FLCSPs) that are commonly used in engineering applications. This study focuses on FLCSPs manufactured using vacuum-assisted resin infusion technology, investigating the scarf repair of impact-damaged FLCSPs. For low-velocity impact and compression after impact tests, three specimen groups, including pristine (undamaged), damaged, and repaired specimens, were designed. Through comparative analysis, the impact response and impact damage of the repaired structures were studied, along with the influence of different impact energies on the impact response and residual compressive strength. The results demonstrate that the maximum impact load of repaired structures can reach more than 90% of that of pristine specimens, while compressive strength can recover to over 85% of the original level, indicating a relatively high recovery level under the present test conditions. In addition, considering the progressive damage mechanism of composite materials, a finite-element model of FLCSPs was established. The numerical model captured the main trends of the impact response and dominant damage modes, providing an engineering-level tool for interpreting the damage and failure mechanisms.