Dielectric strength: dependent or independent of stretch？

 Dielectric elastomer can undergo giant deformation, but are susceptive to various failure modes. i.e electrical breakdown.

Some experimental papers (Kofod, Plante, Chen, see the attachment) reported the dielectric strength of VHB material (a kind of dielectric elastomer) under difference pre-stretch, equal bi-axially or unequal bi-axially. And the strength (maximum voltage can be applied before breakdown) has be greatly improved by these mechanical stretches.

 So here comes the question: is the dielectric strength dependent or independent of stretch？

 For ideal rubbery material, the dielectric strength is a material constant, and should not be affected by the change in thickness.

However, if the VHB films are fully stretched, beyond kind of a threshold value,  the material will stiff sharply, and behave like a rigid ceramic sheet capacitor(maybe an improper description) , then the dielectric strength will increase a lot.

 Therefore, the dielectric strength is closely related to the stiffness of the material, maybe some nonlinear functions, and I am seeking to solve the problem combining our experimental data and theory from polymer physics. So far a rough model is under development

If you guys have some comments, please be free to reply to me.

attachment are some papers about experimental measurement, thanks to Plante and Kofod.