Controllable thermal expansion of large magnitude in chiral negative Poisson's ratio lattices

Abstract

Lattices of controlled thermal expansion are presented based on planar chiral lattice structure with Poisson's ratio approaching −1. Thermal expansion values can be arbitrarily large positive or negative. A lattice was fabricated from bimetallic strips and the properties analyzed and studied experimentally. The effective thermal expansion coefficient of the lattice is about α=−3.5×10−4K−1. This is much larger in magnitude than that of constituent metals. Nodes were observed to rotate as temperature was changed corresponding to a Cosserat thermoelastic solid.

Micro-Structured Two-Component 3D Metamaterials with Negative Thermal-Expansion Coefficient from Positive Constituents

“…1a has an effective Poisson’s ratio of v  =  − 0.41. However, in general, the sign of the thermal-length expansion coefficient is not necessarily the same as the sign of the Poisson’s ratio15.…”

“…Theoretically, the thermal length-expansion coefficient and the Hall coefficient have been discussed1231415161718192021. Regarding the Hall coefficient, even one constituent material A and voids within suffice20.…”

“…Concrete blueprints for three-dimensional structures showing isotropic behavior were suggested later14. Refinements and two-dimensional macroscopic model structures composed of bimetallic beams were published as well1516171822. Discussed theoretically a related two-dimensional structure composed of bimetallic strips showing a negative effective compressibility (at fixed temperature).…”

Auxetics and other systems of “negative” characteristics

“…A few new three‐dimensional (3D) models of dilational materials are presented as well as examples of perfectly auxetic systems, which are considered by the author as non‐dilational. One of these non‐dilational systems, known as a hexachiral auxetic, is the subject of three following papers .…”

“…In the first of them Chan Soo Ha, Eric Hestekin, Jianheng Li, Michael E. Plesha, and Roderic S. Lakes use hexachiral auxetic lattices of PR approaching –1 to obtain systems of arbitrarily large, controlled positive or negative thermal expansion . Examples of such systems, made from bimetallic strips by the authors, which correspond to Cosserat thermoelastic solids, indeed show highly negative thermal expansions.…”