Multi-functional cylindrical metastructures to simultaneously program both thermal expansion and Poisson's ratio

Currently reported cylindrical metastructures mainly act as the load-bearing components, or only present the single function of programming either Poisson's ratio (PR) or coefficient of thermal expansion (CTE). Here, by curling the planar metamaterials, a series of multi-functional cylindrical metastructures is originally devised to simultaneously incorporate programmable CTE and PR. The deformation characteristics are systematically analyzed. It is identified that the number of circumferential cells N remarkably affects the deformation characteristics. When N is small, the warp effect induced by the curved members is remarkable. The quantitative analysis figures out that when N is larger than specific critical values, the PR and CTE of the cylindrical metastructures approach to those of the planar metamaterials. Thus, a design strategy is identified, namely, with adequate circumferential cells, both the PR and CTE of the cylindrical metastructures are independent on the variable N, and are equal to those of the corresponding planar metamaterials. Most importantly, by modulating the geometric parameters, the PR and CTE of the devised cylindrical metastructures can be simultaneously programmed to be wide ranges. The excellent programmability in both PR and CTE enables the cylindrical metastructures to be potentially used in engineering applications where precise control of deformation induced both by mechanical and thermal loads is in urgent need.