Identification of Poisson's ratios of standard and auxetic low-density polymeric foams from full-field measurements

This exploratory paper presents some preliminary results on the use of full-field deformation measurements on low-density polymeric foams to identify the evolution of Poisson's ratio with compressive strain. Two types of foams were tested: a standard low-density polyurethane foam and an auxetic foam manufactured from a similar precursor. Two-dimensional digital image correlation was used to measure the strain field at the specimens' surfaces. Then, Poisson's ratios were identified using a dedicated inverse method called the virtual fields method (VFM) and the results compared with the standard approaches. The results illustrate the advantages of the VFM compared to the standard procedure. It was also found that for the standard foam, very strong localization effects resulted in biased Poisson's ratio evaluation. It was shown that this could be corrected by taking into account these localization effects thanks to the full-field information.