Composite Structures | 2019
Composite microstructures with Poisson’s ratio sign switching upon stress reversal
Abstract
Abstract A rectangular-cells with triangular array and a triangular-cells with rectangular array composite microstructures are introduced herein, which can exhibit Poisson’s ratio sign switching upon reversal of applied stress direction. Each of these microstructures consists of short rigid rods and long flexible rods held together by pin joints. The choice of microstructures permits them to be converted into either conventional or auxetic microstructural geometries depending on the collective deflection patterns of the long flexible rods. Specifically, the microstructures convert into conventional and auxetic ones when loading causes the long flexible rods to deflect outward and inward, respectively. The same consideration applies in the case of thermal expansion analysis, which leads to positive and negative thermal expansivities under constraint condition. Generated results were made on the basis of moderately large deflection analysis and buckling analysis. A greater range of applications can be made on a single structure when it can exhibit greatly differing, or even opposing, properties under loadings of opposite directions.