Hello everyone,

As reported in some references, Maxwell stress of a dielectric  elastomer subjected to electric field can be determined by the following formula

P=e*E^2    (1) -------e=e0*e1, e0 is the dielectric permittivity of vacuum, e1 is the relative dielectric permittivity of the elastomer, and E is the applied electric field.

However I found another expression from  “Electrodynamics of Continuous Media”. (Landau and E.M. Lifshitz.,Course of Theoretical Physics. Vol. 8. 2nd Edition. Butterworth-Heinemann. Oxford. 1984. L.D. ), which is  described as follow,

(sigma)ik=(e/4/pi)(EiEk-1/2E^2 deltaik)     -(2)   pi=3.14