Crash-worthiness studies on multistage stiffened honeycomb core sandwich structures under dynamic impact loads

Abstract

The high-velocity impact performance of honeycomb sandwich structures is enhanced by adopting multi-stage structures with varying cell wall thickness, and cell wall inclination, after preserving the structural mass. The performance of the enhanced structures is simulated considering bullet penetration tests. The penetration is observed to be reduced by 4.82% in case of two stage sandwich structures, as compared to the single stage sandwich structures. Furthermore, the reduction in penetration is estimated to be up to 11.34% when the cell wall thickness is increased from 0.05 mm to 0.15 mm. Moreover, honeycomb cores are stiffened using ribs in two different configurations, within the available space. The improvement in crash-worthiness is estimated by measuring the penetration of the single and two stage hybrid sandwich structures. The penetration distance of stiffened single and two stage structures is found to be reduced by 28.4% and 31.97%, respectively, as compared to the corresponding structures without stiffeners. On the other hand, inclination of the cell walls at an angle to the normal of the face plates is found to enhance the stiffness, and hence the penetration resistance. The honeycomb sandwich structure with oblique unit cells is estimated to dissipate three times more energy as compared to a regular structure. As a result, the impactor is unable to pierce through the sandwich structure. Therefore, two stage hybrid sandwich structures with oblique hexagonal unit cells are recommended for energy absorption in impact applications.