Determination of the hyper-viscoelastic model parameters of open-cell polymer foams and rubber-like materials with high accuracy

Abstract

This paper focuses on a newly-developed method for the extraction of the accurate hyper-viscoelastic model parameters of open-cell polymer foams and rubber-like materials. Although the parameter identification method is developed for strain-controlled uniaxial tension/compression, the finite time increment-based approach used can be extended to other experimental loading modes, such as simple and pure shear, biaxial tension/compression, and confined compression. Furthermore, the method makes it possible to use any hyperelastic material model and to extract the constitutive model parameters of both compressible and incompressible hyper-viscoelastic solids subjected to arbitrary strain (stretch) history. The applicability of the method and the reliability of the constitutive model parameters determined from the numerical prediction of the stress response are proved through the comparison of finite element and measurement results. Finally, the material model parameters of an incompressible isoprene rubber and a compressible polyurethane foam extracted with the proposed method and those determined with the two-step and the direct (closed-form) method are used to compare the accuracy of the predicted behaviours. It clearly revealed that the constitutive constants extracted using the proposed direct (numerical) method result in the best agreement between the measurement and the simulation.