ENTROPY ELASTICITY OF ISOTROPIC RUBBER-LIKE SOLIDS AT FINITE STRAINS

This paper presents a macroscopic continuum formulation and a numerica l analysis of constitutive equations (for stress, entropy and heat flu x) describing the thermoelastic behavior of amorphous cross-linked pol ymers above the glass transition temperature in which a specimen typic ally 'snap-back' with rubbery characteristics. The introduced coupled thermomechanical functional extends the classical strain energy functi on proposed by Ogden. Volume changes due to thermal expansion are rega rded for a large temperature domain and play a remarkable role in ther moelastic materials. The non-linear thermoelastic problem is solved wi thin a staggered (fractional-step) method which is based on a two-phas e (isentropic) operator split. Each of the two symmetric sub-problems retains the characteristic dissipative structure of the implicit monol ithic scheme which consequently results to an unconditionally stable p roduct formula algorithm. The numerical analysis side shows in particu lar the capability of the theoretical framework reproducing the realis tic physical stress-deformation-temperature relations of rubber. Disti nctive attention is paid to the thermoelastic inversion phenomena, a r emarkable property governing the class of rubber-like materials.