On the Lifetime Characterization of Dielectric Elastomer Transducers

Dielectric Elastomer Transducers (DETs) are deformable capacitors that can transform electrical energy into mechanical energy and vice versa. DETs are generally considered as light, flexible structures with good energy density, and have been utilized in applications as actuators, generators and sensors. The main component in a DET system is the Dielectric Elastomer (DE) material, which is a highly elastic dielectric polymer. To verify the feasibility of DET applications, electromechanical properties of DE materials and reliability of DET systems should be thoroughly explored. This thesis focused on the investigation of electromechanical properties of DE materials and lifetime characterization of DET specimens. Three DE materials have been considered for electromechanical characterization: THERABAND YELLOW 11726 styrenic rubber, OPPO BAND GREEN 8003 natural rubber and VHB 4905 acrylic elastomer. DET specimens based on two DE materials have been considered for lifetime characterization: THERABAND YELLOW 11726 and WACKER ELASTOSIL® 2030, a commercialized silicone elastomer. Electromechanical characterization has been conducted according to existing standards, while for lifetime characterization, a novel experimental setup and procedure have been proposed. This proposed methodology makes it possible to perform reliable and efficient lifetime experiments on standardized custom-prepared DET specimens under high voltage operating condition. A series of tests have been conducted following the proposed methodologies and the obtained results have been collected and analyzed. In particular, comparison has been made between the three DE materials considering dielectric and mechanical behaviors. A Gent-Gent model has been found to be able to describe the observed mechanical behavior of considered DE materials. Lifetime results on the styrenic DET specimens have shown, for the first time, how operating conditions and system configuration affect the lifetime behavior of DET systems. For silicone DET specimens, promising lifetime values (over 2 million operating cycles) have been observed under an operating condition with energy density larger than 300J/kg.