A hyperelastic isotropic model with Poisson’s ratio greater than one half

In this contribution, we propose a hyperelastic isotropic material model whose stress–strain response is non-linear even at infinitesimal deformations and cannot thus be linearized. As a result, the superposition principle does not apply and the generalized Hooke law is not valid even at small strains. A further unusual feature of this material model is that Poisson’s ratio can be greater than 0.5 0.5 in full agreement with the laws of thermodynamics. In particular, for the proposed strain energy function, a value of ν =0.644 ν = 0.644 is reached. The model response appears to be plausible in various deformation states such as uniaxial tension/compression, simple shear, and pure dilation.