Electro‐Thermal model of thermal breakdown in multilayered dielectric elastomers

Abstract

Energy transduction of dielectric elastomers involves minute electrical and mechanical losses, both of which potentially increase the temperature within the elastomer. Thermal breakdown of dielectric elastomers occur when heat generated therein cannot be balanced by heat loss on the surface, which is more likely to occur in stacked dielectric elastomers. In this article an electro‐thermal model of a multilayered dielectric elastomer able to predict the possible number of layers in a stack before thermal breakdown occurs is presented. Simulation results show that point of breakdown is greatly affected by an increase in surrounding temperature and applied electric field. Furthermore, if the stack diameter is large, thermal insulation of the cylindrical surface is a valid approximation. Two different expressions for the electrical conductivity are used, and it is concluded that the Frank‐Kamenetskii expression is more conservative in prediction of point of breakdown than the Arrhenius expression, except at high surrounding temperature. © 2018 American Institute of Chemical Engineers AIChE J, 65: 859–864, 2019

Electro‐thermal and ‐mechanical model of thermal breakdown in multilayered dielectric elastomers

“…The elastomer material simulated in this work is a polydimethylsiloxane (PDMS) elastomer, specifically Bluestil RTV 141 from Blustar Silicones 40 , with a thermal conductivity of k 0.16 W/(mK) and a relative permittivity of r 2.7 40 . In our previous work 38 , we found that the electrical conductivity of the PDMS elastomer could be described by an Arrhenius expression with respect to temperature T :…”

“…It should be noted that in Christensen et al 38 , the material used to determine σ Arr was also a PDMS elastomer, but specifically Elastosil RT625 from Wacker Chemie AG.…”

“…A parameter study is conducted in which it is examined how many layers it is possible to stack in a multilayered DE before thermal breakdown occurs, N BD , when varying one given parameter from the base case while maintaining the remaining parameters. As stated previously, the base case geometries in this work are R A 50 cm and R I 0 cm, and base case operating conditions are V 3.5 kV and T 0 15 C. Furthermore, three different hyperelastic material models for the elastomer material in the ETM model are compared, as well as compared to the pure ET model -hence the case with Joule heating but no mechanical deformation, as specified in Christensen et al 38 .…”

“…However, to the best of our knowledge, the number of studies looking into thermal breakdown in DEs is very limited. Previously, we set up a finite-element electro-thermal (ET) model to examine the effect of Joule heating in multilayered DEs 38 . A simplified analytical model was set up and solved, and a parameter study of some key parameters were conducted to determine how they influenced the possible amount of layers in a stacked DE.…”

Temperature dependence of dielectric breakdown of silicone-based dielectric elastomers

“…The maximum magnitude of the breakdown strength is observed as 132 V/ µm for RT625+ RM130 F at 80°C, which, for this corresponding enhancement, is 43% higher compared to the breakdown value of 92 V/µm at 20°C. At elevated operating temperatures, the thermal conductivity and thermal degradation of the silicone dielectric are crucial in determining the point of thermal breakdown [44]. Furthermore, the maximum breakdown strengths for the RT625+ R420, LR3043+ RM130 F, and LR3043+ R420 systems are observed to be 108 V/µm (40°C), 178 V/µm (50°C), and 174 V/µm (40°C), respectively ( Figure 5), while the maximum corresponding enhancements for the same are found to be 24 %, 16 %, and 6 %, respectively ( Figure 5).…”