Abstract
Metamaterials are architected materials with tunable mechanical properties, which makes them suitable for demanding engineering applications. This work addresses two classes of mechanical metamaterials: polymeric materials for energy absorption and impact mitigation, and metallic materials for battery casing. In both cases, the design is formulated as an optimization problem where the objective function represents the desired macroscopic response and the design variables define the internal topology of the metamaterial, subject to stress, geometric, and manufacturability constraints.
For polymeric metamaterials, two advanced concepts for impact mitigation were taken as references: the origami honeycombs of Townsend et al. (Materials & Design, 2020) and the plate lattice metamaterials of Smith et al. (Advanced Materials Technologies, 2024). These architectures were unified into a single parametrized design. The objective was to maximize absorbed energy while limiting peak stress. The objective function was evaluated through post processing of Abaqus results for compression tests on automatically generated designs. Selected samples were fabricated by fused filament fabrication using TPU and tested to validate the numerical predictions. An evolutionary optimization algorithm was employed, restricted to a small number of evaluations due to high Abaqus licensing costs. The results highlight the role of buckling in reducing initial peak stress and of contact interactions in enhancing post peak energy absorption.
For the metallic metamaterial, inspired by the truss based battery casing proposed by Huang et al. (Acta Mechanica Solida Sinica, 2021), optimization targeted either minimal deformation of the central battery cavity or minimal compliance. The design variables were the truss cross sections, and optimization used the method of moving asymptotes. The whole computational framework was implemented in the free Octave package. Structures were fabricated by laser powder bed fusion using AlSi10Mg powder. Compression tests revealed brittle behaviour unsuitable for battery casing applications, although the optimized structures achieved very low compliance, indicating potential as lightweight, high stiffness materials.