Multifunctional mechanical metamaterials with tunable double-negative isotropic properties
Zuyu Li, Wei Gao, Nicole Kessissoglou, Sebastian Oberst, Michael Yu Wang, Zhen Luo
Abstract
This research was focused on innovative design of lattice metamaterials that can exhibit tunable double-negative mechanical properties and elastic isotropy simultaneously. A discrete topology optimization method using a multi-material ground structure was developed to create microlattices exhibiting both negative thermal expansion coefficient and negative Poisson’s ratio in a single integrated design, while maintaining elastic isotropy. First, the numerical homogenization method with beam elements was used to estimate the effective thermal and elastic properties of a microlattice. Second, the topological design, subject to required geometric constraints, was formulated as a mixed integer programming problem to discover a series of multi-material microlattices that present customized isotropic values of negative thermal expansion coefficient and negative Poisson’s ratio. Finally, several three-dimensional multi-material microstructures were produced by altering either the cross-sections or constituent materials of struts to demonstrate their tunable mechanical properties.