Constitutive modeling of the cyclic dissipation in thin and thick rubber specimens
Résumé
A thermo‐viscoelastic‐damage constitutive model, in accordance with the thermodynamic principles, is proposed to describe the cyclic dissipation in rubbers. The general form of the model can be represented by a thermal branch responsible for the stress‐free thermal expansion joined to parallel mechanical multi‐branches responsible for the cyclically damaged‐elastic response and the inelastic effects, i.e. fatigue‐induced stress‐softening and hysteresis. The viscoelastic and damage dissipations contributing to heat build‐up are considered in the model formulation using the internal state variable theory. The model is identified and verified using experimental observations on stress‐softening, hysteresis and dissipative heating obtained on rubber flat specimens containing different amounts of carbon‐black and cyclically loaded under different minimum stretch levels. The model is then used to predict damage and thermal patterns in thick specimens involving different triaxial stress states in the median cross‐section.