Evidence of negative Poisson's ratio in wood from finite element analysis and off-axis compression experiments

Abstract

The microstructure of wood is highly anisotropic, which suggests that this material could exhibit unusual elastic properties. A few studies have suggested the possibility of auxeticity, or negative Poisson's ratio (NPR) in some wood samples. In order to conclusively confirm that wood does show NPR, we have used a combination of geometric modelling, finite element analysis (FEA) and off-axis compression testing. The geometric model indicates that idealised thin-walled wood cell structures should generate NPR of −1, FEA suggests that more realistic cell arrays can attain NPR, to −0.27, and compression tests show that some NPR – to −0.74 – remains in real wood samples. These results could help design “engineered-wood” laminates products with tailored elastic properties.