Architected Lattices with a Topological Transition

Abstract

Topological metamaterials showing two- or multistep deformation under compression provide highly tunable stress–strain responses. A contact-enabled mechanism is incorporated into lattice structures through substituting the regular struts to obtain a global multidirectional two-step deformation. The proposed mechanism is a longitudinal structure with different beams designed for bending or buckling in different stages of deformation. When axially compressed, the mechanism shows a standalone two-step response, which can be widely tuned by varying its geometric parameters. The presence of the mechanisms in different orientations allows for multidirectional functionality, which signifies the uniqueness of this method. By conducting experiments on 3D-printed samples and finite element simulations, the working principle and functionality of the mechanism and lattices in 2D and 3D are shown. It is also explored how the lattice connectivity affects the performance of the topological lattices, and concluded that high enough connectivity of a lattice to achieve stretching-dominant behavior is required for the metamaterial to achieve two-step deformation.