Explicitly Modeling Stress Softening and Thermal Recovery for Rubber-like Materials

Rubber-like materials exhibit stress softening when subject to loading–unloading cycles, i.e., the Mullins effect. However, this phenomenon can be recovered after annealing previously stretched sample under a stress-free state. The aim of paper is establish constitutive model with thermodynamic consistency account for and thermal recovery. Towards goal, (i) an explicit form Helmholtz free energy found such that restrictions from law satisfied; (ii) compressible, multi-axial strain-energy function considering dissipation proposed by introducing specific invariants; (iii) unified shape based on symmetry property test data in one-dimensional case recovery provided weight variant; (iv) it proven new potential automatically reduce case, uniaxial tension, equal biaxial, or plane strain; (v) numerical results validation are exactly matched classical experimental data.