Characterizing the dielectric elastomer’s complete mechanical behavior through an electromechanical coupling method

Abstract

The complete hyperelastic behavior of dielectric elastomers (DEs) refers to the large-range non-linear behavior under multiple loading modes, including uniaxial extension, biaxial extension, and triaxial-stressed deformation. Using hyperelastic models to encapsulate the complete behavior has always been hard due to not only the lack of measurement methods but also the incompleteness of the hyperelasticity theory. Among these obstacles, measuring the equi-biaxial behavior has been a crucial one as the existing methods fail to balance the measuring accuracy and the easy popularization. In this paper, an electromechanical coupling method (EMC method) is proposed to characterize the DE materials with the expectation of both a better complete-behavior coverage and a simpler experimental setup. The proposed method takes a theoretical investigation into the equi-biaxially pre-strained circular dielectric elastomer actuator (PCDEA) and deduces a special form of stress-strain relationship to bridge the gap between the easy-to-setup PCDEA experiments and model characterization. Experiments are then carried out on the classical VHB4910 acrylic film, and various hyperelastic models are evaluated with the proposed EMC characterization method on their fitting capability. Among these models, the Ogden 2-terms model fits all sets of measured data well. Validations are then carried out via DE actuators under more complex loading modes and the EMC-characterized Ogden 2-terms model provides precise behavior predictions with an average $R^2$ of 97.2 %. Thus, this research not only offers useful insights for a more practical complete-behavior-characterization method, but also provides a hyperelastic model for VHB4910 which is worthy of reference.