Compressible rubber materials: experiments and simulations

Abstract

Porous rubber materials are often used in automotive industries. In this paper, a carbon black-filled one is investigated, which is used, for example, as sealing. Such materials are distinguished by viscoelastic behaviour and by a structural compressibility induced by the porous structure. To identify the material behaviour, uniaxial tension tests and hydrostatic compression tests are performed. Therein the main focus of attention lies on the basic elasticity and on the viscoelasticity in the whole loading range. An important observation of these tests is the viscoelastic behaviour under hydrostatic compression, which has to be included in the material model. Because of the two-phase character of cellular rubber, the theory of porous media is taken into account. To model the structural compressibility, a volumetric–isochore split of the deformation gradient is used. Therein the volumetric part includes the aspect of the point of compaction. Finally, the concept of finite viscoelasticity is applied introducing an intermediate configuration. Because of the viscoelastic behaviour under hydrostatic compression, the volumetric–isochore split is taken into account for the nonequilibrium parts, too. Nonlinear relaxation functions are used to model the process-dependent relaxation times and the highly nonlinear behaviour with respect to the deformation and feedrate. The material parameters of the model are estimated using a stochastic identification algorithm.