Low velocity impact response of gradient foam-CFRP honeycomb sandwich structure fabricated by the integrated molding method

This study presents a novel method for the integrated molding of foam and carbon fiber reinforced polymer (CFRP) honeycomb core. This method enhances the previously complex manufacturing process of foam-filled honeycomb structures and facilitates the pre-design of foam to expand the multifunctional application scenarios of the structure. It can efficiently construct gradient foams with a wider absorption bandwidth within honeycomb cavities, simultaneously improving the structure's impact resistance. A combined experimental–numerical approach, incorporating impact testing and a finite element model, is employed to investigate the influence of impact energy, foam density, and density gradient on structural performance. The results reveal that the CFRP honeycomb primarily governs the initial peak load, while the foam contributes more significantly to overall energy dissipation. Increasing the foam density alters the phase-wise energy absorption behavior and modifies the honeycomb failure mode. Distinct failure patterns are observed for foams with positive and negative density gradients, with the negative gradient configuration demonstrating superior impact resistance compared to uniform-density foam of equivalent mass.