A note on the multiscale volume changes of auxetic metamaterials assessed via digital image correlation

The present manuscript approaches the mechanical interpretation about the volume changes of auxetic metamaterials within a multiscale perspective. The kinematic fields resulting from the mechanical tests were assessed via digital image correlation (DIC). The multiscale mechanical characterization is grounded within sound homogenization principles based on representative volume elements (RVE) at large deformations. The main achieved results concern in highlight that even though the Poisson's ratio still widely used to characterize the mechanical behavior of auxetic metamaterials, it does not represent a suitable variable to quantify the multiscale volume changes, mainly when finite deformations take place. In this regard, a proper homogenized kinematical quantity is used in this work. Moreover, statistical tools are employed aiming at a better understanding to what extent the multiscale kinematics influence the volume changes and the overall auxetic behavior of the material.