Relation of bulk to shear loss factor of solid viscoelastic materials

The relation between the bulk and shear loss factors of isotropic, homogeneous, linear solid viscoelastic materials is investigated in this paper by means of the complex modulus concept. It is shown that the bulk and shear loss factors can be related through the dynamic Poisson's ratio provided that the shear loss is low enough. Bounds on the ratio of the bulk to shear loss factor are derived, and the respective lower bounds are given as a function of the dynamic Poisson's ratio. The ratio of the bulk to shear loss factor is predicted to decrease with the increase of dynamic Poisson's ratio, and it is shown that the decrease may obey a simple power law if the Poisson's ratio is close to either 0 or 0.5. Experimental data on solid polymeric materials are presented which support the theoretical findings.