Continuum electro-mechanical damage modelling for dielectric elastomer

Dielectric Elastomer Transducers (DETs) represent an emerging technology with great potential for mechatronic applications. DETs allow to convert electrical energy into mechanical energy and vice-versa, making it possible to design actuators, generators, and sensors. These devices show many advantages like high energy density, silent operations, and low cost, but their practical applicability is strongly affected by their reliability and lifetime, which depend on both environmental conditions and electro-mechanical loads. Theoretical and experimental studies have recently been initiated to investigate the lifetime ranges of such devices for different loading conditions (e.g., mechanical, electrical, electromechanical). At present, the lifetime characterization of DETs has been conducted by means of stochastic models only. In principle, a better understanding of electro-mechanical fatigue mechanism of DETs can be obtained through an appropriate analysis of their underlying physics. In this context, this paper presents a novel modeling approach for electro-mechanical damage evolution of DETs. In order to describe the phenomena involved in the damage process in physically consistent way, a free-energy framework is adopted. Starting from well-established electro-mechanical free-energy functions, additional variables which account for both mechanical and electrical fatigue mechanisms are introduced. Singular models for damage accumulation are developed and integrated within the free-energy conservation principle, in order to dynamically simulate the life status of the dielectric material when subjected to combined electric and mechanical loads. Finally, the kinetic law for damage evolution history due to combination of different failure modes are introduced, and used to assess DETs reliability based on experimental observations