Comparisons on the Local Impact Response of Sandwich Panels with In-Plane and Out-Of-Plane Honeycomb Cores

The influence of in-plane and out-of-plane element array effects of honeycomb on the impact characteristics of sandwich panels was studied under different local impact speeds. The numerical model is calibrated by air cannon impact experiment and used to conduct the investigations. It is demonstrated that the sandwich panel with in-plane honeycomb core (SPIH) exhibits a response mode with larger local indentation and smaller overall deflection, and also shows superior energy absorption as compared to the sandwich panel with out-of-plane honeycomb core (SPOH). When facing more severe impact conditions, SPIH shows better anti-penetration capability. When the impact radius is 20 mm and the impact velocity is 83 m/s, the SHOP is penetrated while the SHIP is not. When the impact radius is 20 mm and the impact velocity is 100 m/s, the total absorbed energy of SHIP is 59.79% higher than that of SPOH, and the impact residual velocity is 32.67% lower. Furthermore, the impact mitigation performances of SPIH with different density gradient cores are investigated by comparing their deformation modes and energy absorption characteristics. The results indicate that different gradient schemes enable sandwich panels to perform multiple functions. The positive gradient design in the cell stretching direction is beneficial to reduce the overall deflection and improve the energy absorption effect