Numerical stress solutions for the accurate calibration of hyper-viscoelastic material models of polymer foams

Abstract

Proper calibration of material models is one of the essentials of a reliable numerical prediction. It is particularly critical in numerical simulation of highly compressible hyper-viscoelastic solids such as polymer foams. In this study, new finite time increment-based stress solutions are presented for the case when the time-independent behaviour is defined by the generally accepted modified Ogden model (also known as hyperfoam model) while the time dependence is described by the Prony series-based linear viscoelastic model. The stress solutions give the basis of the parameter identification method proposed with which even the temperature-dependent behaviour may be taken into consideration. The following simple loading modes are considered: uniaxial/equibiaxial compression, confined uniaxial/equibiaxial/volumetric compression and simple shear. The stress solutions are then used to identify the material parameters of a compressible, open-cell polyurethane foam. The results demonstrate the capability of numerical stress solutions in calibrating hyper-viscoelastic material models with high accuracy on the basis of any loading mode presented or simultaneous consideration of various loading modes.