Three-dimensional auxetic porous medium

We propose the design of a novel three-dimensional porous continuous solid exhibiting negative Poisson’s ratio. The shape and periodic distribution of the pores guarantee cubic symmetry, and the directional dependence of the Poisson’s ratio and Young’s modulus shows a moderate degree of anisotropy and multidirectional auxeticity. We demonstrate the auxeticity of the porous solid numerically, solving both a periodic analysis on a unit cell and a boundary value problem on a finite specimen. The numerical results are fully confirmed by experimental results, obtained from Digital Image Correlation data. The final parametric analysis indicates how to modulate the characteristic parameters of the microstructure in order to tune macroscopic properties. The proposed design maintains a relatively high Young’s modulus and it is prone to large-scale industrial production.