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This paper focuses on the characterisation of the vibroacoustic response of dielectric elastomer (DE) membranes. We set our attention on a circular DE membrane, deformed three-dimensionally and mounted in between fixed frames, which is able to generate sound with no need for any elastic or pneumatic biasing element. We present a finite element model of the system entirely based on commercial software Comsol Multiphysics. The model combines: 1) a mechanical model of the DE membrane, which makes use of suitably defined energy functions that account for electro-elastic coupling; and 2) an acoustic model of the domain surrounding the DE. The model implements a bi-directional coupling between the DE and the acoustic domain. In particular, it accounts for the effect of the acoustic pressure loads applied on the DE membrane, which, given the small thickness and low density of the membrane, play a significant role in the system dynamics. We validate the model against experimental measurements of the DE surface velocity and the sound pressure level (SPL) in the surroundings of the membrane. Despite relying on strong simplifications in the geometry of the system and the viscous response of the material, the model is able to describe the main trends in the device frequency response, and how the SPL varies as a function of the mechanical pre-load and the voltage applied on the membrane.

Dielectric elastomers (DEs) consist of thin membranes of dielectric material (e.g., silicone) coated with compliant electrodes. When subject to a high voltage, a DE undergoes an in-plane expansion which can be used for actuation purposes. Nowadays, most of the applications of DE actuators (DEAs) are based on single-degree-of-freedom systems. If many DEA elements are combined together in an array-like structure, a new generation of distributed and cooperative micro-actuators can be developed, with potential applications in fields such as soft robotics, distributed acoustics, and wearables. In this work, we present the first steps towards the development of such types of cooperative DEA systems. In particular, we report a finite element (FE) simulation study conducted on a one-dimensional array of silicone-based DEAs. Individual activation of each actuator in the array can be performed in an independent way, thus allowing to implement cooperative control paradigms. First, a FE model of the system is implemented in COMSOL environment and validated by means of experimental data. Then, a simulation analysis is conducted with the aim of understanding how the system parameters (e.g., geometry, pre-stress, actuators spacing) affect the overall electro-mechanical performance. The presented analysis will serve as a reference for the development of distributed cooperative DEA systems.

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