Robust lightweight multifunctional thermally tailored lattices

Abstract

This paper presents conceptual designs for lightweight lattices that are able to connect two materials with differing coefficients of thermal expansion without generating thermal expansion mismatch stresses during temperature excursions. The lattices operate passively at ambient conditions to accommodate large variations of temperature and to provide constant separation, independent of temperature, between the substrate materials. When pin-connected, the lattices are free from thermal mismatch stresses both internally and at their connections with the substrates. However, previous configurations of these lattices are highly sensitive to small perturbations in geometry, as would be associated with thermal expansion or manufacturing imperfections, and hence must be designed giving consideration to such phenomena. Hence, sensitivity analysis must be a factor in the design process. To show that such sensitivity analyses can be carried out using theoretical approaches, experimental results are presented that are in accord with the theoretical calculations. Several examples are given to demonstrate strategies for reducing lattice sensitivity to geometric imperfections for different combinations of material and geometry. More importantly, novel alternative designs for lattices using simpler configurations, which are less sensitive to small perturbations, are explained. These alternative lattices employ less complicated geometry and, in some cases, require only one material, but offer less adaptibility in the situations to which they are applicable.