Abstract
An analysis of the thermomechanical behavior of the natural rubber is carried out by combining two quantitative imaging techniques. The digital image correlation of visible images is used to estimate the strain and then the deformation energy whereas infrared images make it possible to estimate, via the heat equation, the amounts of heat involved in the material transformation. The construction of energy balance enables us to determine the relative importance of the dissipative and thermomechanical coupling mechanisms. For low frequency and low extension ratio, the results show the famous thermoelastic inversion effect. From an energy standpoint, a competition between entropic elasticity and stress-induced crystallization/fusion mechanisms is observed for more significant extension ratios. No significant dissipative effect can be detected at low or high loading frequency whereas in each case, a stress-strain hysteresis characterizes the cyclic response of the material.