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A schematic (sectional view) showing the experimental setup, which has a DEA sample completely immersed in a silicone oil bath while the DEA is activated by high voltage.
Electromechanical activation of DEAs in either the air or the oil immersion: (a) Photographs showing electrode expansion for a DEA when tested in air. Wrinkles and sparks at spot were observed on dielectric film when the DEA breaks down at 11 kV (or 450 MV/m). (b) Photographs showing electrode expansion for a DEA when tested in the silicone oil immersion. Wrinkles appear changing from mild to severely undulated and sagging as the driving voltage increases from 11 kV to 18 kV, but the oil immersed DEA did not break down. (c) A graph showing areal strain of the activated DEAs as a function of electric field until breakdown.
Thermography of the activated DEAs: (a) two thermograms of a DEA sample in air at 10 kV and 11 kV, respectively. The right thermogram showed that a hot spot occurred at the puncture when the DEA in air breaks down at 11 kV. (b) two thermograms of silicone oil bath, which immerses a DEA sample that is activated at 18 kV and 19 kV, respectively. Right thermogram showed that a distorted hot spot happens on the oil surface and it indicates oil circulation and Joule' heating at the puncture of DEA, which breaks down at 19 kV.
Monitor of temperature and leakage current for DEA samples, which were activated by increasing voltages in air or oil immersion, respectively. (a) A graph showing temperature as a function of driving voltage at the punctured region of DEA sample. (b) Time histories of leakage current as the driving voltage is ramped up across the DEA. Leakage current surges when DEA breaks down. (c) Time histories of the driving voltage, which was increased incrementally until the breakdown of DEA. The voltage dips to low beyond the control when DEA breaks down in air at 11 kV.
(a) Temperature dependence of volume (or bulk) resistivity of a 200% biaxially pre-strained VHB 4905 film (with a 55 μm pre-stretched thickness). (b) Surface resistance of graphite powder electrodes as a function of uniaxial stretch ratio.
Breakdown strength of VHB films or DEAs.
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