ABSTRACT
Filled rubbers are often submitted to cyclic loadings. The presence of fillers increase stiffness and lifetime but at the same favor the Mullins softening. On top of that, when submitted to a large number of cycles, filled rubbers experience some cyclic softening that cannot be neglected. Both softenings should be taken into account in an effort to predict the mechanical properties of rubber structures submitted to fatigue. Therefore, we looked at the particular properties of the mechanical behavior of softened filled rubbers. For this purpose we submitted a carbon-black filled styrene butadiene to cyclic loadings at various maximum stretches and up to 1000 cycles. We took a close look at the Mullins effect induced stress-strain responses and at the stress-stretch cyclic responses. Then, several models reported in the literature and designed to reproduce the Mullins softening were tested with more or less success. Finally, a simple model framework is proposed to account for the Mullins induced residual stretch and the cyclic softening. This framework is shown to adapt to any of the Mullins softening model of the literature and prove to be supported by the experimental evidences.
