Abstract: ObjectivesThis 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 back 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 back panel deformation characteristics of Y-type sandwich structures using the ABAQUS finite element simulation software Meanwhile, the back panel deformation and failure modes obtained from simulation results were compared and analyzed with the experimental results. Results It is found that the numerical simulation results are in good agreement with the experimental results. Compared with steel structures of the same mass, the damage degree of the rear panel of the Y-type sandwich structures is significantly reduced, which can effectively suppress the maximum transverse deformation of the rear panel, and the structural integrity is remarkably improved.Conclusions This study can provide a certain reference for the research on the dynamic impact response of Y-type sandwich structures.