Dielectric Elastomers: An Investigation in Strain Dependent Electrostatic Pressure of Soft Compliant Dielectric

Dielectric elastomer actuators (DEA) have the potential of exhibiting large strains when the material is in the presence of an electric field. The dielectric in this case is a soft acrylic (VHB 4910) film that is sandwiched between two complaint electrodes that are subjected to a high voltage potential. When high voltage is applied, attracting charges lead to a contractive force known as electrostatic pressure. The electrostatic pressure deforms the elastomer membrane and the contraction occurs in the thickness (z-plane) direction, which leads to actuation and expansion of the film. The pressure in the z-direction is usually governed by electrostatic pressure from Pelrine [1]. In Pelrine's model the relative permittivity is assumed to be constant when calculating for pressure. Recent research has found that relative permittivity changes as the DEA material is stretched [1]. The trend has shown the permittivity decreases as stretch rates increase. From a microscopic level, polarization within the DEA determines the materials permittivity, making it deformation dependent. This work will look to investigate theoretically and experimentally polarization dependent electrostatic pressure model. Using the GR 1689/1689M measuring system the permittivity of the DEA as a function of stretch can be solved for. This data will be collected and used in a best fit curve to determine the permittivity ranges of the DEA from its relaxed state to a maximum deformation state.