VHB

The dielectric constant is an essential electrical parameter to the
achievable voltage-induced deformation of the dielectric
elastomer. This paper primarily focuses on the temperature
dependence of the dielectric constant (within the range of 173 K
to 373 K) for the most widely used acrylic dielectric
elastomer (VHB 4910). First the dielectric constant was investigated
experimentally with the broadband dielectric spectrometer
(BDS). Results showed that the dielectric constant first increased
with temperature up to a peak value and then dropped to a
relative small value. Then by analyzing the fitted curves, the Cole–Cole
dispersion equation was found better to characterize the
rising process before the peak values than the Debye dispersion

Dielectric elastomer transducers are often subject to large tensile stretches and are susceptible to rupture. Here we carry out an experimental study of the rupture behavior of membranes of an acrylic dielectric elastomer (VHB 4905). Pure-shear test specimens are used to measure force-displacement curves, using samples with and without pre-cracks. We find that introducing a pre-crack into a membrane drastically reduces the stretch at rupture. Furthermore, we measure the stretch at rupture and fracture energy using samples of different heights at various stretch-rates. The stretch at rupture is found to decrease with sample height, and the fracture energy is found to increase with stretch-rate.
This paper has appeared in the Journal of Applied Physics and can be downloaded from:

The dielectric constant of elastomeric dielectric material is an
essential physical parameter, whose value may affect the
electromechanical deformation of a dielectric elastomer actuator. Since
the dielectric constant is influenced by several external factors as
reported before, and no certain value has been confirmed to our
knowledge, in the present paper, on the basis of systematical comparison
of recent past literature, we conducted extensive works on the
measurement of dielectric properties of VHB films, involving five
influencing factors: prestretch (both equal and unequal biaxial),
electrical frequency, electrode material, stress relaxation time and
temperature. Experimental results directly show that the dielectric