CONSTITUTIVE APPROACH TO RATE-INDEPENDENT PROPERTIES OF FILLED ELASTOMERS

Filled rubber material is used in many technical applications. These s tructures are often subjected to dynamic loading. Apart from the mater ial's stiffness characteristics dissipative properties are of great im portance. At high frequencies rubber material behaves mainly viscoelas tically. But at low strain-rate the response is nearly rate-independen t, This observation can be interpreted as ''internal material friction '' and is dealt with in the following article. A constitutive approach is presented, which can be motivated by investigations on the molecul ar level. This phenomenological description is composed of an elastic model-idealized as an elastic spring- and elasto-plastic Prandtl-eleme nts in parallel. The formulation is derived for small and finite strai ns. The large strain case is based on a multiplicative decomposition o f the deformation gradient. Experimental results and numerical simulat ions are presented utilizing a mixed finite element formulation to giv e a robust algorithm and reliable results. (C) 1998 Elsevier Science L td.