ABSTRACT
The physical mechanisms involved in the deformation of natural rubber are numerous and are still the object of keen scientific debate, among them viscosity, strain-induced crystallization and crystallite melting, cavitation, as well as energetic and entropic effects on the thermomechanical response. To investigate these physical deformation processes, several experimental techniques have been used, including X-ray diffraction (Katz 1925, Toki, Fujimaki, & Okuyama 2000), X-ray microtomography (Legorju-Jago 2007), dilatometry (Ramier, Chazeau, Gauthier, Stelandre, Guy, & PeuvrelDisdier 2007) and classic mechanical tests such as stress relaxation and cyclic tests. Any deformation process induces heat production or absorption that
reason is that the temperature field is influenced by heat conduction as well as heat exchanges with the ambient air and the grips of the testing machine used. In rubbery materials, which undergo large deformations, only two studies have recently been carried out to develop motion compensation techniques in the case of heterogeneous tests (Pottier, Moutrille, Le Cam, Balandraud, & Grédiac 2009, Toussaint, Balandraud, Le Cam, & Grédiac 2012). These studies focused on the numerical post-treatment of temperature fields, and were not dedicated to the analysis of the deformation processes. The present paper aims therefore at applying quantitative calorimetry to characterize and to analyze the thermomechanical behaviour of natural rubber under homogeneous uniaxial tensile tests, at ambient temperature.
