We propose a protocol to model accurately the electromechanical behavior of
dielectric elastomer membranes using experimental data of stress-stretch and
voltage-stretch tests. We show how the relationship between electric
displacement and electric field can be established in a rational manner from
this data. Our approach demonstrates that the ideal dielectric model,
prescribing linearity in the purely electric constitutive equation, is quite
accurate at low-to-moderate values of the electric field and that, in this
range, the dielectric permittivity constant of the material can be deduced from
stress-stretch and voltage-stretch data. Beyond the linearity range, more
refined couplings are required, possibly including a non-additive decomposition
of the electro-elastic energy. We also highlight that the presence of vertical
asymptotes in voltage-stretch data, often observed in the experiments just
prior to failure, should not be associated with strain stiffening effects, but
instead with the rapid development of electrical breakdown
