Compression-induced failure of electroactive polymeric thin films

Abstract

The insurgence of compression induces wrinkling in actuation devices based on EAPs thin films leading to a sudden decrease of performances up to failure. Based on the classical tension field theory for thin elastic membranes (e.g.[11]), we provide a general framework for the analysis of the insurgence of in-plane compression in membranes of electroactive polymers (EAPs). Our main result is the deduction of a (voltage-dependent) domain in the stretch space which represents tensile configurations. Under the assumption of Mooney-Rivlin materials, we obtain that for growing values of the applied voltage the domain contracts, vanishing at a critical voltage above which the polymer is wrinkled for any stretch configuration. Our approach can be easily implemented in numerical simulations for more complex material behaviors and provides a tool for the analysis of compression instability as a function of the elastic moduli.Keywords: actuators, electroactive polymers (EAP), compression instability, non-linear elasticity.The growing interest in electroactive polymers as actuator devices, ranging from medical, biological, robotic, and energy harvesters, results from their qualities such as lightweight, small size, low-cost, flexibility, fast response [8,7,3]. A typical device consists of a thin sheet of electroactive polymer sandwiched between two compliant electrodes. The simple mechanism of actuation releases on an electromechanical coupling of the Coulomb forces acting between the electrodes and the elastic forces inside the layer. The electrostatic forces acting on the sheet faces induce a transversal extension that is used as a mean of actuation.In this paper we are mainly concerned with compression induced insta-

Stability analysis of charge-controlled soft dielectric plates

“…The large actuation achieved due to the snap-through behaviour is desirable for many applications but is difficult to achieve in practice. Snapthrough is often prevented by electric breakdown [29] or by instabilities such as inhomogeneities [1], compression failure [5], band localisation [10], wrinkles [17,20,21,28,24,3], membrane wrinkling [12], etc.…”

Nonlinear electroelasticity: material properties, continuum theory and applications

“…Theoretical analysis of electromechanical instability has been considered by many authors, exemplified in [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. Based on the theory of small deformations superimposed on large deformations for a general electroelastic material following the development of Dorfmann & Ogden [43], an analysis of the stability of an electroelastic plate was performed by the same authors in [44].…”

“…The counterpart of (7.35) for the energy function Ω * , with variables λ 1 , λ 2 and K 4 is denoted Ω * (λ 1 , λ 2 , K 4 ) and obtained by specializing (7.7) as 37) whereω * (λ 1 , λ 2 ) =ω(λ 1 , λ 2 ) and λ…”

Damage induced dissipation in electroactive polymer harvesters

“…3,4,22,23,30 The working principle of electromechanical harvesters is based on the idea that a part of the mechanical work done to deform a thin EAP membrane, sandwiched between compliant electrodes, can be used to pump electric charges from lower voltage to higher voltage: this is achieved by making use of filler-reinforced materials with enhanced elastic stiffness and dielectric permittivity. 22,23,25 Despite the positive features described above, the performances of electromechanical harvesters are affected by several limitations, spanning from the dielectric breakdown threshold of the EAP material, 2 to the occurrence of wrinkling and pull-in instabilities, [10][11][12]26,28 to the localization of deformations, 13,29,34 to the dissipation in the loading frame of the membrane, 22 and finally to dissipation processes taking place at the level of the polymeric material. This last aspect plays an important role in harvesting applications and the present analysis is devoted to its modelling.…”