A new design for enhanced stiffness of dual-constituent triangular lattice metamaterial with unbounded thermal expansion

Abstract

Multifunctional lattice metamaterial with high stiffness and a wide range of tailorable coefficient of thermal expansion (CTE) is desirable in many engineering structural application subjected to large fluctuation in temperature. Dual-constituent triangular lattice metamaterial composed of completely bi-layer curved rib elements (called the Lehman-Lakes lattice) has unbounded thermal expansion; however, its stiffness has a substantial decrease due to the initial curvature of rib element. In this study, a new double-curve rib element is proposed, in which the two curve parts are asymmetric and the layer one is partially covered by layer two in every curve part. Then, the dual-constituent triangular chiral lattice metamaterial (DTCLM) composed of the newly designed rib elements is presented in order to improve its stiffness. When the used materials are considered to be invar and steel, compared with the Lehman-Lakes lattice, the new proposed DTCLM with zero CTE has about 2.9 times improvement in stiffness; when achieving the same large positive or negative CTE, the stiffness has also obvious improvement. Besides, the thermomechanical analysis of the new proposed DTCLM is given by the closed-form analytical solution. The effectiveness of the analytical models and the optimized results are verified by the detailed numerical simulation.