Schwarzite-inspired hybrid cellular structures for energy absorption applications

Abstract

Inspired by Schwarzites, a novel hybrid cellular structure is proposed for energy absorption applications. The Schwarzite-inspired unit cell is reinforced by introducing a stiffener in its open region, which is further enhanced by incorporating an extruded geometry (referred to as an “extruder”) within the stiffener to maximize energy absorption. Structural optimization is carried out using quasi-static crush analysis, leading to the selection of the optimized unit cell 2 (UC2) for all subsequent studies. The impact resistance of the proposed unit cell is evaluated through bullet impact simulations, targeting pre-selected weak points on a sandwich structure composed of a UC2 core and Aluminum faceplates. This configuration demonstrates resistance to bullet velocities of up to 115 m/s at arbitrary impact locations. Subsequently, the Aluminum faceplates are replaced with carbon fiber reinforced polymer (CFRP) faceplates featuring various ply orientations. The use of CFRP results in a maximum reduction in bullet penetration depth of 17.81%. Among the different configurations, the [0/90/0/90] cross-ply orientation exhibits the least penetration depth and is therefore recommended. Finally, air blast simulations are conducted on sandwich structures incorporating cores made from UC2, bamboo spiderweb (BS), hierarchical honeycomb (HH), and stiffened honeycomb (SH) designs. Among these, the UC2 core exhibits the highest bending stiffness and the lowest back-face deflection, indicating uniform structural stiffness. Consequently, this design eliminates the need for multi-stage layering or strategic core offsetting.