Numerical analysis of the dynamic response of C/C−PMI sandwich panels under low-velocity impact loading

This study aims to investigate the dynamic response and damage evolution mechanisms of sandwich structures composed of woven C/C laminates and polymethacrylimide (PMI) foam under low-velocity impact loading, and to clarify the effects of impact energy and key structural parameters on their mechanical performance.

A numerical simulation model was developed, in which a progressive damage model for the composite laminates was implemented using a VUMAT subroutine, while the PMI foam was modeled using a crushable foam plasticity model that accounts for strain rate effects. A systematic investigation was conducted on the dynamic response of the sandwich panels under low-velocity impact, quantitatively evaluating the influence of the foam core's strain rate effect on the simulation results. Furthermore, a sensitivity analysis was performed on the key structural parameters of the sandwich panel.

The results indicate that neglecting the strain rate effect leads to a significant underestimation of the dynamic load-carrying capacity of the sandwich structure. The primary failure mechanisms of the C/C−PMI sandwich panels include matrix tensile failure, matrix compressive failure, and foam core crushing. Plastic crushing of the PMI core serves as the dominant energy dissipation mechanism, accounting for 82.3% of the total energy absorption. The maximum indentation depth increases nonlinearly with impact energy, and a transition from non-penetrating damage to local penetration occurs at approximately 60 J under the present configuration. The core-to-face-sheet thickness ratio is identified as the most influential structural parameter; energy absorption efficiency increases significantly as the ratio increases to 8.25, whereas further increases promote premature face-sheet penetration and localized core crushing. For naval engineering applications, a core-to-face-sheet thickness ratio of approximately 8.25 is recommended for energy-absorbing structures. For decks and bulkheads where global load-bearing capacity and damage tolerance are prioritized, a lower ratio is preferable, with greater emphasis on increasing the thickness of the front face-sheet.

The results provide a reference for the impact-resistant design and safety assessment of lightweight composite ship structures.