Material Characterization of Strain Rate Dependent Elastomers using Simplified Rubber Material Model in LS-DYNA

Elastomers are widely used in many automotive components such as seals, gaskets etc., for their hyperelastic properties. They can undergo large strain and can return to their original state with no significant deformation making them suitable for energy dissipation applications. Most common testing procedures include uniaxial tension, pure shear, biaxial tension and volumetric compression under quasi-static loading conditions. The results from these tests are used to generate material models for different finite element (FE) solvers, such as LS-DYNA. Commonly used material models for elastomers in LS-DYNA are the Ogden Material Model (MAT77), which uses parameter-based approach and the Simplified Rubber Material Model (MAT181), which uses tabulated input data. Prediction of rate dependent behavior of elastomers is gaining interest as, for example, during a crash simulation the components undergo impact under different strain rates. Hyperelastic models such as MAT77 enable rate dependency prediction through stress relaxation data (Prony series). Identifying optimum values for the material parameters is often time consuming, iterative and involves additional testing. This paper explores the possibility of rate dependent prediction using a much simpler tabulated stress-strain based methodology in MAT181 and also analyzes the impact of model parameters such as bulk modulus, shear modulus, damping coefficient, Poisson’s ratio, etc., as the baseline values sometimes lead to model instabilities. The work focuses on materials which experience large strain under simple tension. Material models are validated by comparing results from FE simulations with tensile test data.