Effect of mechanical pre-stretch on the stabilization of dielectric elastomer actuation

Abstract

A dielectric elastomer is capable of giant electromechanical actuation but fails at breakdown due to instability under certain conditions with a small deformation. By applying a mechanical pre-stretch, one obtains a stabilized large actuation. In this paper, we measured the dielectric constant and critical voltage of a polyacrylic dielectric elastomer subjected to both equal and unequal biaxial stretch, and modelled its actuation by employing the Gent strain energy function with a microscopic view to characterize the nonlinear stiffening behaviour and the electrostrictive effect in the deformation. The mechanical pre-stretch contributes in several ways to the stabilization of dielectric elastomer, by eliminating the pull-in instability, by generating electrostriction, by improving the breakdown strength, as well as by reducing the membrane thickness which consequently lowers the voltages required for activation.

Investigation into the electromechanical properties of dielectric elastomers subjected to pre-stressing

“…Kofod [23] proved that dielectric strength and electrostatic force were greatly increased by modelling cuboid DE actuators using VHB 4910 which has a relative permittivity of about 4.7. It was also found that the pull-in instability, which significantly affects the electrical performance of DEs, can be eliminated by applying a pre-stretch [24][25][26][27]. An investigation of the influence of pre-stretch on the electromechanical properties of DEs by using VHB 4910 and DEs based on silicone rubber containing BaTiO 3 is presented here.…”

Manipulating torsional motions of soft dielectric tubes

“…Subsequently, torsional waves propagating on top of the resultant configuration are analyzed. The significance of the mechanical constraints in the response of soft dielectrics, well-known for the static regime, [21][22][23][24] is explored in this setting. Related problems were treated in purely elastic annular cylinders.…”

“…Conversely, by applying boundary constraints the tube resistance to breakdown increases and the loading path extends, in agreement with related works. 21,23 Therefore, the loading path includes configurations consisting of a sufficient charge to trigger the velocity jump. Further, a comparison of the curves associated with different axial constraints explains why when tensile strain was applied less voltage was needed, as a lower value was sufficient to reach the steep segment of the curve.…”

Fabrication of transmissive dielectric elastomer actuator driven tunable optical gratings with improved tunability

“…Also, the prestretch eliminates the electromechanical instability of the membrane and allows for high actuation strain. 29 Upon actuation, the electrodes expand and the passive region contracts in length, thereby reducing the period of grating in this region. The strain in the passive region is considered the negative of S, modified by a geometric parameter that depends on the electrode geometry.…”