On the anisotropic and negative thermal expansion from dual-material re-entrant-type cellular metamaterials

• Published in: Journal of materials science Vol. 52; no. 2; pp. 899 - 912
• Main Authors: Ng, Chun Kit, Saxena, Krishna Kumar, Das, Raj, Saavedra Flores, E. I.
• Format: Journal Article
• Language: English
• Published: New York Springer US 2017; Springer; Springer Nature B.V
• Subjects: Analysis; Anisotropy; Braze welding; Cellular structure; Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; Composite materials; Crystallography and Scattering Methods; Electronic components; Finite element method; Material properties; Materials Science; Metamaterials; Original Paper; Poisson's ratio; Polymer Sciences; Public radio; Solid Mechanics; Struts; Thermal expansion; Thermal properties; Triangles; Beam Element; Stiffness Ratio; Metamaterial Structure; Negative Thermal Expansion; Anisotropic Thermal Expansion
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-016-0385-7

Negative thermal expansion (NTE) and negative Poisson’s ratio (NPR) are counterintuitive material properties that have gained popularity as the focus of many recent works. However, most of the structures previously studied only exhibit NTE or NPR exclusively. One important structure that has already been shown to exhibit NPR is the re-entrant triangle. In this work, the property of NTE in re-entrant triangular cellular structure composed of welded/bonded/brazed ribs of two different materials is investigated via analytical and finite element (FE) modelling. Based on analytical and FE analysis, the geometrical and material parameters for attaining NTE in the re-entrant metamaterial are established. The analysis and simulations reveal the dependence of NTE on the inclination of the longer chevron strut, the dimensionless rod coefficient of thermal expansion (CTE), the ratio of thermal expansion coefficients of constituent struts but independent of scale and temperature. The extent of this property becomes more negative for higher values of the angle of the longer chevron strut with the vertical, higher ratios of CTE of the base to chevron strut material and for lower values of the non-dimensional re-entrant base material thermal expansion coefficient. The anisotropic and NTE behaviour is stretch-dominated. Effectively, combined with previous knowledge of NPR in the re-entrant triangle, NTE leads to further significance of such structures for many thermal and mechanical applications, such as composite materials, sensors and electronic components industries in both thermal and mechanical applications.