New electromechanical instability modes in dielectric elastomer balloons

Under the actions of internal pressure and electric voltage, a dielectric elastomeric membrane mounted on an air chamber can deform to a balloon shape. Due to the nonlinear deformation, snap-through instability can happen in the balloon, which has been harnessed to achieve giant voltage-triggered deformation. In addition to the snap-through instability, with an applied voltage, a new electromechanical instability mode with a localized bulging-out in the balloon has been recently observed in experiments. However, the reported phenomenon has not been well explained. In this article, through numerical computation, we obtain the relation between the volume of the balloon and its internal pressure, when the balloon is subjected to different voltages. We find out that when the applied voltage is small, the pressure vs. volume diagram of a balloon can be represented by an N-like curve, which is similar to the conventional hyperelastic balloon only subjected internal pressure; when the voltage is larger than a critical value, new instability modes in the balloon emerge, which have a localized bulging-out, similarly to the shape observed in the experiments. We further show that the critical voltage for the new instability mode of the DE balloon is closely associated with the prestretches applied to the membrane and the hyperelastic model for the elastomer.