4D Printing of Digital Structure Toward Programmable Buckling and Superior Metamaterial

Mechanical metamaterials have attracted great research interests due to their extraordinary mechanical properties and urgent demands. However, there are few of works on digital structures (DSs) reported, where the DS could provide a programmable structure-design manner and extendable applications for the metamaterials. This study proposes a new type of DS, in which the circular-hole units work as the negative Poisson’s (NP) parts to drive the compression–bucking coupling, while the square-hole units work as the positive Poisson’s (PP) parts to achieve a predictive buckling trial. Based on the strain continuity principle, a Poisson’s ratio model is initially formulated to investigate the deformation behaviors of the DS. Then, finite element method (FEM) simulations are carried out to reveal the influences of gradient arrangement and structural volume fraction on the buckling behaviors in 3D printing DSs. These simulation results reveal that the negative–positive–negative (NPN) arrangement is applicable to enhance the buckling stability and programmable trial of DS, of which the buckling trials are stemmed from interlayer-driven and intercell-driven, respectively. Finally, the experimental measurements have been conducted on the two types of DSs, where the experimental results are in a good agreement with FEM ones.