Objectives This study aims to investigate the dynamic response and failure mechanism of composite Y-type sandwich structures in the field of impact resistance.

Methods Three types of composite Y-type sandwich structures with different relative densities were fabricated via a mold hot-press molding process, and foam aluminum projectile impact tests were conducted using a one-stage light-gas gun device. The effects of different relative densities on the impact resistance of composite Y-type sandwich structures were analyzed through experiments. The influence of impact intensity on structural failure modes was explored and the dynamic response process of the structures was studied based on the deformation of the rear panels. A finite element model for the dynamic impact response of composite Y-type sandwich structures was established to analyze the dynamic response process, damage modes and rear panel deformation characteristics of Y-type sandwich structures using the ABAQUS finite element simulation software Meanwhile, the rear panel deformation and failure modes obtained from simulation results were compared and analyzed with the experimental results.

Results The results show that increasing the relative density of the composite Y-type sandwich structure from 2.73% to 7.95% reduces the maximum deformation of the rear panel by 45.8% under low-intensity impact. Compared with steel plates of the same mass, the deformation of the rear panel of the Y-type sandwich structure is reduced by 38.2%–56.5%. In addition, recommendations for the optimal relative density selection are proposed for different impact intensities.

Conclusions The research results clarify the matching relationship between structural relative density and impact strength, providing a direct basis for the optimal design and engineering selection of this type of sandwich structure in shock-resistance protection for naval vessels.