This paper contains a thorough investigation of the performance of electrically activated
layered soft dielectric composite actuators under plane deformation. Noting that the activation
can be induced by controlling either the voltage or the surface charge, the overall behaviour of
the system is obtained via homogenization at large strains, taking either the macroscopic
electric field or the macroscopic electric displacement field as independent electrical variables.
The performance of a two-phase composite actuator compared to that of the homogeneous
case is highlighted for few boundary-value problems and for different values of stiffness and
permittivity ratios between constituents being significant for applications, where the soft
matrix is reinforced by a relatively small volume fraction of a stiff and high-permittivity
phase. For charge-controlled devices, it is shown that some composite layouts admit, on one
hand, the occurrence of pull-in/snap-through instabilities that can be exploited to design
release-actuated systems, and on the other hand, the possibility of thickening at increasing
surface charge density.
