What is Poisson's ratio?
silver.neep.wisc.edu › ~lakes › PoissonIntroFurther interrelations among elastic constants for isotropic solids are as follows. B is the bulk modulus. The theory of isotropic linear elasticity allows Poisson's ratios in the range from -1 to 1/2 for an object with free surfaces with no constraint. Physically the reason is that for the material to be stable, the stiffnesses must be positive; the