Constitutive Model of Filled Elastomers Capable of Capturing Mullins Effect, Hysteresis, Induced Anisotropy and Permanent Set – Part II: Experiments & Validation

This contribution discusses experiments necessary to describe the behavior of filled elastomers under large strains. Filled elastomers show a variety of inelastic phenomena such as Mullins effect, hysteresis, induced anisotropy, and permanent set. While uniaxial tension tests to rupture provide virgin loading curves, other tests are necessary to gather information about the inelastic effects mentioned above. In order to capture these phenomena experimentally, cyclic uniaxial tension tests with stepwise increasing load amplitudes are carried out. Since experimental stress-strain curves characterize some restricted set of defined loading conditions (such as uniaxial test, pure shear, or equi-biaxial tension), additional investigations of two-dimensional strain data from arbitrary deformations states are necessary. This strain data can be obtained for example by digital image correlation. In particular, we demonstrate how the previously described constitutive model can be calibrated using a variety of experiments. We verify the calibration comparing the results of our subroutine implemented as UMAT in LS-DYNA with two-dimensional strain data obtained from digital image correlation of a plate with a hole subjected to tension. The described model shows good agreement with the obtained data.