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

Methods A numerical simulation model was established, incorporating a progressive damage model for the composite laminates implemented via a VUMAT subroutine and a crushable foam plasticity model for the PMI foam considering strain rate effects. A systematic investigation was conducted on the dynamic response of the sandwich panels under low-velocity impact, quantitatively analyzing 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.

Results The results indicate that neglecting the strain rate effect severely underestimates the dynamic load-carrying capacity of the sandwich structure. The primary failure mechanisms of the C/C-PMI sandwich panels include matrix tension, matrix compression, and foam core crushing. The plastic crushing of the PMI core acts as the primary pathway for energy dissipation, accounting for 82.3% of the total energy absorption. The maximum indentation depth increased nonlinearly with impact energy, and a transition from non-penetrating damage to local penetration occurred at about 60 J under the present configuration. The core-to-face-sheet thickness ratio was identified as the dominant structural parameter; the energy absorption efficiency increased significantly when the ratio increased to 8.25, whereas a further increase promoted premature face-sheet penetration and localized core crushing. For naval engineering applications, a core-to-face thickness ratio of about 8.25 is recommended for energy-absorbing structures. For decks and bulkheads prioritizing overall load-bearing and low damage, a lower ratio is preferable, prioritizing the thickening of the front face-sheet.

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