Experimental and simulative characterization for material and lifetime modelling of a silicone adhesive

Abstract Material and lifetime modelling of silicone adhesives has become more and more important due to their wide application in building and automotive industry. To find the most crucial material parameters for lifetime prediction, an elastomeric silicone adhesive is characterized with different thermomechanical methods. Above the first-order phase transition from crystalline to amorphous state at about -40 °C the frequency and temperature dependence for small and large strains is negligible and the time-temperature superposition principle cannot be used for extrapolation to other temperatures or frequencies. The first stretch invariant at break is independent of strain rate and shows a reciprocal temperature dependency, i.e. fracture energy can be provided by thermal and strain energy. Maximum principal strain is identified as a suitable failure criterion for different load cases and strain rates for static loading as well as for fatigue. Long-term stress relaxation behavior follows a power-law with stretch-dependent pre-exponential factor and exponent. Using compressibility from a hydrostatic pressure experiment, a hyperelastic material model is used to describe the quasistatic stress-stretch curves for different load cases at 23 °C with strain rates of 0.01 s−1. Validation experiments show good agreement for two joint geometries with multiaxial load cases.