A visco-hyperelastic model with Mullins effect for polyurethane elastomers combining a phenomenological approach with macromolecular information

Abstract

The classical generalized formulations for nonlinear viscoelastic behaviour do not represent the state of the art of modelling elastomeric materials and significant effects observed on polyurethane elastomers are not accurately predicted such as the loss of stiffness and the presence of residual strain by the Mullins effect. In this context, the present work proposes a model building strategy for visco-hyperelastic materials with Mullins effect merging a phenomenological approach with a macromolecular one. Polyurethane elastomers are modelled as a composite material consisting of crystalline and flexible phases. The dissipative effects observed in the viscoelastic behaviour are then related to the reorganization of the microstructural crystalline domain during the deformation process. Adding a softening parameter to the viscous strain rate predicted by Bergstrom–Boyce viscoelastic model led to more accurate predictions when describing the mechanical behaviour of these materials. The proposed model strategy is assessed based on measured data obtained from Polyurethane elastomers of different hardness under monotonic tensile tests and cyclic tensile tests. The model built with the proposed approach provided predictions closer to measured data than the predictions provided by the model solely based on phenomenological aspects for the analysed cases.