Deformation study of an in-plane oscillating dielectric elastomer actuator having complex modes

Due to the deformation ability over a wide frequency range, dielectric elastomer actuators (DEAs) under an alternating electric load have received increasing attention. In the theoretical analysis of an in-plane oscillating DEA (edge clamped membrane without a pressure load), the assumption of homogeneous deformation is applied, which conflicts with the observed non-uniform deformation under a combination of pressure and voltage load. To validate the simplification, experimental and theoretical studies of a circular DEA under alternating voltage are reported here. A laser Doppler vibrometer is used to acquire the full-field oscillating response of the DEA fabricated by commercial VHB4905 with hydrogel electrodes. The measured amplitude and phase illustrate that the assumption of homogeneous deformation only works at low frequencies, whereas the non-uniform deformation dominates the oscillation with the increase of excitation frequency. In addition, the in-plane oscillating DEA behaves as a complex mode system. Accordingly, the motion equation is proposed by considering the general viscous damping effect. The experimentally observed transition (from uniform to non-uniform deformation) is analyzed numerically. The normalized upper frequency, under which the deformation field can be treated as uniform, is also obtained based on full-wave simulations.