Non-Linear Poisson Function for Natural Rubbers

—In linear elasticity, Poisson’s ratio is one of the physical constants which characterizes an isotropic material, as it describes its lateral contractive response in infinitesimal strain. It has been proved that the use of this constant is limited, for several application where a material is subjected to large deformation. In this case, a scalar function of deformation can be defined, known as Poisson’s function, but the strain tensor must be calculated first. Due to various existing strain tensors, several Poisson’s functions are calculated to describe the negative strain tensor in the orthogonal direction, divided to the strain tensor in the axial direction, where the force is applied. Selected experimental tests are performed for elastomers under simple tension and the resulting Poisson’s functions are shown for different strain tensors.