Design and analysis of mechanical behavior of a novel lattice auxetic structure based on rigid rotating mechanism

Auxetic materials with negative Poisson’s ratio, as a group of metamaterials, attracted significant attentions among researchers due to their interesting and remarkable mechanical properties. Rigid rotating structures are a subcategory of auxetic materials which can show the same behavior in various directions by tuning their parameters, but due to using rigid rotating blocks their relative density is high. As the rotating blocks are connected by weak joints, stiffness and strength of these structures are low and considering high relative density of these structures specific mechanical properties are even in worse condition. In this research, novel lattice structures based on rigid rotating structures but with remarkably lower relative density were presented. To reduce relative density of these structures, bar elements were used instead of rigid blocks. 3D printing method was used to manufacture samples with these structures and then tensile test was performed on the samples. Poisson’s ratios of the samples were measured by recording image of the structures before and during deformation. The behavior of the structures was predicted by finite element method and compared with experimental measurements. Both of the methods showed auxetic behavior of the structures. Then deformation mechanism of the structures and the effect of the structures shape on the auxeticity were investigated.