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M. Krommer:
"Nonlinear electro-elastic shells: Modelling and stability analysis";
Talk: 13th International Conference on Theoretical and Computational Acoustics , ICTCA 2017, Vienna (invited); 2017-07-30 - 2017-08-03.

In the present contribution thin electro-elastic shells undergoing large deformations are studied. Such shells are made of dielectric materials, which can be used for both, sensing and actuation. In particular, we consider two types of materials: (1) Anisotropic piezoeleastic materials, for which the classical linear piezoelectric effect dominates the electro-elastic response, and (2) isotropic dielectric elastomers, in which pondomotive and electrostatic forces in combination with the quadratic electrostrictive effect provide the actuation authority.

Based on the theory of nonlinear electro-elasticity, thin shells are introduced as material surfaces with mechanical and electrical degrees of freedom. The present contribution extends our previous work concerning constitutive coupling. In particular, piezoelectricity and electrostriction are accounted for by means of a hybrid multiplicative / additive decomposition of the deformation measures of the material surface; previously, piezoelectricity was only considered within an additive decomposition and electrostriction was not accounted for at all. The resulting nonlinear electromechanically coupled shell theory is discretized using Finite Elements.

Case studies are presented, in which the electro-active materials are used as actuators to control the deformation of the shell. We are especially interested in problems, in which the actuators are used to control the switching between two non-neighbouring stable configurations of the shell. It will be shown that active switching can be enabled either by means of a snap-through instability or by means of a snap-buckling instability. This is true for both actuator materials, piezoelectric actuators and dielectric elastomer actuators. Stability and post-buckling behaviour are discussed by semi-analytical methods - e.g. the Galerkin procedure - and the results are verified against the numerical Finite Element computations. Possible applications of the discussed systems are e.g. micro-bumps, buckling actuators or highly dynamic switching devices for loudspeakers.