Pull-in and wrinkling instabilities of electroactive dielectric actuators

Abstract

Abstract.We propose a model to analyze the insurgence of pull-in and wrinkling failures in electroactive thin films. We take in consideration both cases of voltage and charge control, the role of prestretch and the size of activated regions, which are all crucial factors in technological applications of EAPs. Based on simple geometrical and material assumptions we deduce an explicit analytical description of these phenomena, allowing a clear physical interpretation of different failure mechanisms such as the occurrence of pull-in and wrinkling. Despite our simple assumptions, the comparison with experiments shows a good qualitative and, interestingly, quantitative agreement. In particular our model shows, in accordance with experiments, the existence of different optimal prestretch values, depending on the choice of the actuating parameter of the EAP.Confidential: not for distribution.

An energetic model for macromolecules unfolding in stretching experiments

“…Here, aimed to a deduction of a continuum model for macromolecular materials [2], we analyse the continuum limit of Figure 5. Unfolding energies as a function of n u deduced from the following experiments: (a) AFM experiment on titin from [14]; (b) AFM experiment on TNfnAll protein from [60]; (c) AFM experiment on titin from [48]; (d) AFM experiment on tenascin-C from [54]; (e) AFM experiment on titin from [59].…”

“…A common property of these materials [2,4,[8][9][10] is that their macroscopic history-dependent, dissipative response is the result of complex evolutions of 'semicrystalline' microstructures. These are constituted by flexible (polymeric or protein) macromolecules reinforced by strong and stiff crystals (e.g.…”

“…Similar considerations can be extended to the next elastic and dissipative steps, so that the total dissipation is Q ¼ P Q i ¼ P [jFj] i . Based on previous considerations and inspired by the model in [2,29], where the authors describe the hysteresis of filled polymers and spider silks, here we propose an energetic approach and describe the unfolding macromolecule as a two-state material. Similarly, a two-state energetic approach was proposed in [30] to describe the helix !…”

Electromechanical phase transition in dielectric elastomers

“…Electromechanical instability has been recognized as a mode of failure for dielectric elastomers subject to increasing voltage (Stark & Garton 1955;Plante & Dubowsky 2006), which limits the amount of energy conversion by dielectric elastomers in practical applications Diaz-Calleja et al 2008;Koh et al 2009Koh et al , 2011Leng et al 2009;Tommasi et al 2010;Xu et al 2010). In particular, an experimental manifestation of the electromechanical instability was reported by Plante & Dubowsky (2006): under a particular voltage, a prestretched dielectric elastomer membrane deformed into a complex pattern with a mixture of two states, one being flat and the other wrinkled.…”

Multiscale instabilities in soft heterogeneous dielectric elastomers

“…Much of the existing work on coupled instabilities is motivated by failure. Examples include the study of pull-in instabilities [33,34], electrical breakdown [8,35] and failure mechanisms at high electric fields [36] in homogeneous media as well as electrical breakdown of DE with random distribution of the inclusions [37,38]. Dorfmann & Ogden [39] wrote the incremental equations of electro-elasto-statics about a finite deformation, and used it to study the stability of homogeneous half-space.…”