Topology optimization of assembled mechanical metamaterials for large-scale structures

Abstract

Mechanical metamaterials have garnered significant attention due to their unique properties, such as low stiffness-to-weight ratio and auxetic behavior. However, the fabrication of large-scale mechanical metamaterials remains challenging due to the limitations of current manufacturing technologies and high costs. This paper proposes a novel topology optimization method for designing assembled metamaterials with extreme physical properties that can be mass-produced and integrated into large-scale structures through mechanical connections, in which the overall structural topology of the assembled microstructures and the location of joints are simultaneously optimized. Several two-dimensional (2D) numerical examples with different extreme properties were presented, and a set of mechanical experiments were conducted to demonstrate that the optimized discretely assembled metamaterials exhibit superior mechanical properties, outperforming even the monolithic structure made of the same metamaterial units. Furthermore, the optimized 2D units were transformed into three-dimensional (3D) configurations by folding them at various angles. Three large-scale macroscopic structural examples were presented to illustrate the cost-effectiveness and high reproducibility of the assembled metamaterials.