Mechanical structures are subjected to ambient vibrations or acoustic pressures which can be used to produce energy using adequate transducers that convert mechanical loadings into electrical polarization. The use of smart materials such as EAP (electro-active polymer) to harvest energy from the mechanical vibrations of the surrounding environment is a recent and promising concept. This study focuses on the characterization and identification of mechanical properties for an elastomer material (VHB 4910 produced by 3M® company) which can be functionalized such as an EAP material for acoustic energy control.
Mechanical tests have been carried out using tensile testing machine (MTS Criterion® Model 45) equipped with a thermo-conditioning device to control the environmental conditions (temperature and humidity). Tensile test have been performed with an imposed loading–unloading displacement speed of 5 mm/s for various temperatures (from ambient temperature to 65 °C). The measured force–displacement data have been filtered by using a moving average method.
The force–displacement response exhibits an energy storage within the material and a dependence on temperature. Assuming incompressibility, three hyperelastic models have been considered : the Neo-Hookean model with one parameter, the Mooney-Rivlin model with two parameters and the Ogden model with six parameters. Each set of material parameters has been identified by using a non-linear inverse method based on Levenberg-Marquardt algorithm. It has been observed that : (1) the Neo-Hookean model does not fit well with experimental data, (2) the Ogden model is more precise than the other ones for low temperatures and (3) the same performance for high temperatures has been obtained with Ogden and Mooney-Rivlin models. Thus, it has been found that the Mooney-Rivlin model is the best compromise between complexity and suitability. The relationship between initial shear modulus and temperature has been approximated by a second-order polynomial with a sufficiently small residual error.