Modelling dielectric elastomer actuators using higher order material characteristics

Dielectric elastomers, a special class of electroactive polymers, have viscoelastic properties that strongly affect their dynamic performance. This paper contributes a high-order linear solid model together with an optimised parameter identification method to aid the selection of the model parameters. The paper also demonstrates that accurate modelling of the viscoelastic characteristics for commonly used dielectric elastomer (DE) material requires additional spring-damper combinations within a standard linear solid model. The effect of key parameters on the system dynamics in the frequency domain is elaborated and used to guide the parameter identification of the models. The increased effectiveness of higher order models that incorporate multiple spring-damper combinations is demonstrated using three experiments; (a) mechanical loading of a stacked sample over 0.01-5 Hz with strain variations up to 50%; (b) mechanical loading of a single-layer sample over 1-100 Hz with strain variations up to 10%; and (c) electrical actuation of a single-layer sample over 1-100 Hz using electric fields up to 20 MV/m. Silicone and polyacrylate samples were tested to show the effect of viscoelastic properties in the frequency domain. The proposed method of parameter identification is optimised to capture the frequency response.