The influences of deformation state and experimental conditions on inelastic behaviour of an extruded thermoplastic polyurethane elastomer

Thermoplastic polyurethane elastomers under cyclic loading–unloading conditions exhibit inelastic effects, mainly stress softening, hysteresis loss and residual strain. In order to discuss the sensitivity of these effects to deformation state (uniaxial tension and pure shear) and to work conditions (maximum strain, strain-rate and stretching direction), this study is concerned with inelastic effects of an extruded thermoplastic polyurethane elastomer when is subjected to loading–unloading cycles. Based on the behaviour of inelastic effects under both tensile conditions, the present work shows that stress softening and residual strain are sensitive to deformation state only when the maximum strain reached causes permanent set. Furthermore, the hysteresis loss shows an independent behaviour depending on maximum strain. Finally, the behaviour of the hysteresis loss and the residual strain is isotropic for the extruded thermoplastic polyurethane elastomer.