Shear, compressive and dilatational response of rubberlike solids subject to cavitation damage

In this paper we examine the change in material response, in particular the dilatational response, due to cavitation damage arising from tensile hydrostatic stresses of sufficient magnitude. A general discussion of stress softening and cavitation is followed by a description of some new experimental results concerning the change in response in hydrostatic tension or compression or in shear due to cavitation damage. In hydrostatic tension there is a progressive reduction in the value of the tensile bulk modulus of the material during loading and significant stress softening on unloading. As a result of the cavitation damage the tensile bulk modulus in the natural configuration is reduced. Ultimately, failure of the material occurs at sufficiently large hydrostatic tension, typically when the volume increase locally exceeds a critical value, of the order of 2–3%. However, the compressive bulk modulus is unaffected by the cavitation damage. Moreover, it is also found that the shear modulus is likewise unchanged by cavitation. The experimental data are used to develop a theoretical model, based on the concept of pseudo-elasticity, to describe these phenomena. Specifically, the dilatational part of the strain-energy function of an elastic material depends on a damage parameter which provides a means for switching the form of the strain-energy function, thereby reflecting the stress softening associated with unloading. A good correspondence between the theory and the data is obtained.