On Pseudo-Elastic Models for Stress Softening in Elastomeric Balloons

The phenomenon of stress softening observed in the cyclic inflation of spherical balloons or membranes is quantitatively and qualitatively examined. A new measure of the stress softening extent is proposed which correctly captures the main feature of this phenomenon. This measure of the stress softening is related to the relevant response functions in the constitutive models proposed in the literature to describe this effect. Using these relationships, the predictive capability of the theoretical models is examined. It is shown that only those theoretical models which admit a non-monotone character of the stress softening can properly describe this phenomenon.