The effects of static pre-stretching on the short and long-term reliability of dielectric elastomer actuators

Pre-stretching membranes in dielectric elastomer actuator (DEA) systems is a widely known technique to improve the dielectric's breakdown strength and therefore enhance the overall device performance. The impact of this approach on the long-term reliability of DEAs is, however, still unknown. In the present work, it is investigated how the elastomer lifetime is affected by the mechanical pre-stretch. Silicone membrane samples with different pre-stretch ratios were prepared and the respective DC dielectric strengths were measured for both short and prolonged tests using methodologies inherited from high voltage assessment technology. It is shown that, despite an absolute beneficial increase of the dielectric strength for the tensioned membranes, pre-stretching has a detrimental effect on the system's useful life. In all the studied cases, the pre-stretched specimens showed a shorter expected lifetime compared to new, relaxed membranes. The results suggest a careful selection of the relative electric field to be applied to DEAs system for long and reliable lifetime. (paper)