Electromechanical instabilities in periodic dielectric elastomer composites

Several types of electromechanical instability emerge in periodic dielectric elastomer (DE) composites either limiting the range of electromechanical actuation or providing an opportunity to harness instabilities for enhanced functionality. The electromechanical pull-in instability - extensively studied in monolithic DEs - is also encountered in periodic DE composites, and additional instability types - microscopic, macroscopic, and interfacial instabilities - arise in DE composites. For general DE composites subjected to arbitrary electromechanical loading, numerical simulation is required to detect all types of instability. In this paper, using a finite-element-based numerical simulation capability, we consider electromechanical instabilities in DE composites consisting of periodic lattices of aligned circular-cross-section fibers embedded in a matrix. We report on several types of electromechanical instabilities that are known to occur in this type of DE composite: (1) pull-in, (2) microscopic, (3) macroscopic, and (4) interfacial instabilities, while surveying a comprehensive parameter space. Namely, the roles of shear modulus contrast, electric permittivity contrast, fiber volume fraction, chain-locking behavior, mechanical prestress, prestretch, and confinement are considered. The result is an overarching view of the instability landscape in periodic, fiber-based DE composites. We conclude by showing that microscopic instabilities may be harnessed to invoke electric-field-triggered pattern transformations in certain cases. (C) 2019 Elsevier Ltd. All rights reserved.