Negative thermal expansion in transversely isotropic space frame trusses

The negative thermal expansion (NTE) of a type of space frame structure is investigated herein. On the basis of a space frame structure consisting of tetrahedral representative volume elements, a volumetric thermal strain and a volumetric coefficient of thermal expansion (CTE) models are developed in this paper. The NTE trusses developed herein exhibit a special case of anisotropy known as transverse isotropy. This is achieved by using two types of rod materials, each for the three apex rods and the three base rods. From these models, the conditions for attaining negative volumetric strain and negative coefficients of volumetric expansion due to change in temperature are established. Two definitions of NTE are given herein: (a) overall NTE and (b) incremental NTE. Based on these two definitions of NTE, the conditions that lead to (i) definite NTE and (ii) selective NTE are established. Plotted results reveal a trend in which the extent of negative thermal expansion is increased for lower apex-to-base rod length and CTE ratios, and higher base rod CTE. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim