Transverse strain of silicone dielectric elastomer actuators

Abstract

Some dielectric elastomers produce large electric-field-induced strains that can be used for electromechanical actuation. When an electric field E is applied on an electroactive polymer film electroded on both sides, the film is subjected to a stress T due to the electrostatic force (Maxwell stress) and this causes it to deform, producing a strain in the plane perpendicular to the applied field. We have measured the transverse strain responses of silicone (Dow Corning HS III) Maxwell stress actuator samples of different sizes over a wide displacement range and a frequency range from DC up to 100 Hz. The static and dynamic strain responses of the materials to a variety of driving electric flelds such as step fields, AC fields and DC bias fields have been measured as functions of amplitude and frequency. The effect of a mechanical tensile pre-load on the transverse strain has also been investigated. A pre-load initially causes an increase in the strain but the strain decreases when larger values of pre-load are applied. Numerical finite element simulations of the material using the commercial software package ANSYS and suitable models of hyperelasticity provide good agreement with most of our observations on the electric field and pre-load dependencies of the transverse strain.