A Simplified Rubber Model with Damage

Simulation of rubber-like materials is usually based on hyperelasticity. If strain-rate dependency has to be considered viscous dampers also have to be taken into account in the rheological model. A disadvantage of such a material model is time-consuming parameter identification associated with the damping constants. With MAT_SIMPLIFIED_RUBBER (Material no. 181), a material law is implemented in LS-DYNA which allows fast generating of input data based on uniaxial static and dynamic tensile tests at different strain rates. However, unloading, i.e. forming of a hysteresis, cannot be modeled easily using Mat181. Thus, an extension of Mat181 based on a damage formulation was desirable. In this paper, we show the theoretical background and algorithmic setup of our model which has been implemented as MAT_SIMPLIFIED_RUBBER_WITH_DAMAGE (Material no. 183) in LS-DYNA. As an application, the validation of a soft and a hard rubber under loading and subsequent unloading at different strain rates is shown.