Finite Deformations of Tubular Dielectric Elastomer Sensors

Abstract

This article describes a numerical model validated with experimental results for a large stretch tubular sensor. The sensor is a dielectric elastomer (DE) membrane with electrical properties that can be accurately correlated with mechanical strain, for strains well over 50%. The DE sensor is a passive capacitive sensor. To illustrate the concept, the sensor is attached to the inner surface of a fiber-reinforced elastomer actuator, which serves as the host substrate. Fiber-reinforced elastomers configured for pneumatic operation are employed as actuators in robotic, prosthetic, and morphing applications. An electromechanical model for the two-layer composite consisting of the fiber-reinforced elastomer and the sensor is derived. For several illustrative loading profiles, the model yields a strain output for an input capacitance value. Using identical loading cases, an experimental setup was designed to measure sensor output for two different sensor materials: silicone and polyacrylate. The sensitivity of the DE sensor was also evaluated for varying geometrical parameters and is mainly dependent on the initial thickness. Comparison of experimental data and numerical results is very good with an overall error of 3—6%. This work shows that the model is robust in the large strain range and furthermore predicts non-linear strain behavior.