Topology Optimization of Sandwich Truss Cores for Improved Plastic Energy Absorption

Abstract Sandwich panels with truss cores (SPTCs) are widely used in crashworthiness and impact-related applications due to their light weight, high load-carrying capacity, and excellent energy dissipation performance. However, most existing design optimization methods for SPTCs are limited to size and shape optimization of the truss bars and often focus solely on linear elastic behavior. In this study, a topology optimization framework to design the core of SPTCs is proposed using the geometry projection method, aiming to maximize plastic energy absorption and minimize deflection under quasi-static loading, while constraining material usage. An elasto-plastic constitutive model is employed to capture the nonlinear material behavior, and an element removal strategy is used to avoid severe mesh distortion and ensure a robust analysis. Design sensitivities are computed using a finite difference scheme, leveraging the relatively low number of design variables describing the bars and circumventing the need for analytical derivatives. The proposed approach is demonstrated through numerical examples, with the optimized designs evaluated against conventional pyramidal truss-core panels. The results confirm the practical applicability and effectiveness of the method for designing protective structures.