Optimisation of a pretreatment method to reach the basic elasticity of filled rubber materials

Filled elastomers usually show a pronounced viscoelastic behaviour with long relaxation times. The basic elasticity of the material represents the basis for the complete viscoelastic material model. The important problem is that the long relaxation times lead to a very difficult experimental procedure in order to get the appropriate experimental data. An adequate pretreatment of the material can significantly reduce the experimental duration. This effect has been seen for different types of filled elastomers and has been investigated in detail for a carbon black-filled ethylene propylene diene monomer (EPDM). In the present work, the single steps in the development of the material model for this EPDM are presented, including the basic elasticity, viscoelastic behaviour for moderate strain rates and the Payne effect as a softening effect. An adequate pretreatment can reduce the experimental duration to get the basic elasticity. By using the material model, an optimisation of this experimental pretreatment process is determined for uniaxial loadings. The result of this optimisation can also be seen for different kinds of filled elastomers. Finally, the question whether these conclusions can also be transferred to biaxial deformations is discussed and experimentally examined.