Characterization and Comparison of the Mullins Effect of Carbon-Black Filled Rubbers at Small and Large Strains

Several carbon-black filled styrene-butadiene rubbers showed different sensibilities to the Mullins softening when submitted to cyclic uniaxial tension. In order to quantify this softening, an original parameter was introduced. It is defined by using a classic damage approach and can be estimated by using either the strain amplification factor method or the tangent modulus at zero stress. Both approaches are compared and prove to consistently lead to similar results. The proposed parameter is used to study the effect of crosslink density and filler amount on the Mullins softening. The latter is shown to remain unaffected by a change of crosslink density and to increase with an increase of filler amount. More interestingly, with the definition use, the damage parameter exhibits a mere linear dependence on the maximum logarithmic strain applied, and on the filler volume fraction. A simple linear expression is given finally to predict the Mullins softening of filled rubbers.