ABSTRACT
ABSTRACT: Rubbers undergo a softening phenomenon called Mullins effect in first cycles of loading which is more pronounced in filled rubbers. Existence of a clear physical interpretation for this effect is of great importance in development of constitutive relations and numerical simulations. In this paper, a network alteration theory is proposed to obtain general form of evolution laws based on the physical description of the material molecular network. It is shown that the number of active monomers in material molecular network is not necessarily a decreasing function of the applied deformation but it can even increase. To find out the physical mechanism responsible for this phenomenon and also to see how it does not contravene the principle of mass conservation, the nature of broken links is investigated with focus on the role of filler particles. It is concluded that, for filled elastomers, the weak physical filler–chain interactions are the main broken links during deformation; hence, their morphology is precisely noticed and inspired by the Langmuir’s theory, fractional evolution laws are formulated. Comparisons of the model results with experimental data show good correlations. It is concluded that, the developed relations well estimate the alterations of the material network and also provide a useful tool for modeling the Mullins–softening.
