In this paper, the characterization and electromechanical stability behavior of nano sized BaTiO<sub>3</sub> particle filled
dielectric elastomer has been analyzed experimentally and theoretically. The free energy function involving a new
dielectric energy density function and Mooney-Rivlin elastic strain energy function has been used to carry out the
analysis. To give a comprehensive dielectric energy function, the influence of the BaTiO<sub>3</sub> weight fraction on the
dielectric property of the dielectric elastomer has been considered. The analytical results show that with the
increasing weight fraction of BaTiO<sub>3</sub> or the electrostrictive factor, the critical electric field of silicone elastomer
decreases, i.e. the elastomer’s stability is reduced. Meanwhile, with the increasing material constant ratio k which is
the ratio of the two material constants appeared in the Mooney-Rivilin elastic strain energy function, the critical
nominal electric field will increase. These results are useful in not only helping us to understand the influence of the
filled nano-BaTiO3 particles on the electromechanical stability of silicone dielectric elastomer, but also giving great
guidance to obtain specific dielectric elastomer actuators to meet the demand of users by changing the dielectric
property of the elastomer.
Silicone rubber is a common dielectric elastomer material. Actuators made from it show excellent activate properties
including very large strains (up to 380%), high elastic energy densities (up to 3.4 J/g), high efficiency, high responsive
speed, good reliability and durability, etc. When voltage is applied on the compliant electrodes of the dielectric
elastomers silicone rubber, the polymer shrinks along the electric field and expands in the transverse plane. In this paper,
a theoretical analysis is performed on the coupling effects of the mechanical and electric fields. A nonlinear field theory
of deformable dielectrics and hyperelastic theory are adopted to analyze the electromechanical field behavior of these
actuators. Applied elastic strain energy function is obtained from the representative Yeoh model. The electric energy
function involves invariant and variable dielectric constant respectively. Then deduce the constitutive relation for the
dielectric elastomer film actuator based on the selected function. Also the mechanical behavior of the dielectric
elastomer silicone rubber undergoing large free deformation is studied. The constitutive modules of dielectric elastomer
composite under free deformation and restrained deformation are derived. The Barium Titanate (BaTiO3) with high
permittivity was incorporated into the raw silicone to fabricate a new dielectric elastomer, the experimental results that
the elastic modulus and dielectric constant were significantly improved. Finally the Yeoh model was developed to
characterize the elastic behavior of the new dielectric elastomer. The constitutive modules of dielectric elastomer
composite under free deformation and restrained deformation are derived. This is a promising analysis method for the
study of the coupled fields and mechanical properties of the dielectric film actuator.
Dielectric elastomers (DEs) are one particular type of electroactive polymers. Dielectric elastomers
work as a variable capacitor. The effects of conductive particles on the actuating behavior of silicone
rubber-based dielectric elastomer are studied in this work. Two different materials, which are carbon
nanotube and carbon black, respectively, are used to increase the overall permittivity of the composites.
Although the addition of these conductive particles increases the permittivity of the composite, they
also produce a highly inhomogeneous electric field and reduced breakdown strength of the composite.
This reduction in breakdown strength could be a serious drawback of nanocomposite approach. The
main challenge, therefore, becomes how to enhance the permittivity of the composite while
maintaining its high breakdown strength. These composites are characterized by dielectric spectroscopy,
tensile mechanical analysis, and electromechanical transduction tests. The effect of variation in filler
loadings on the complex and real parts of permittivity are distinctly visible, which has been explained
on the basis of interfacial polarization of fillers in a heterogeneous medium. The phenomenon of
percolation was discussed based on the measured changes in permittivity and morphology of
composites at different concentrations of these particles.
Dielectric elastomers have received a great deal of attention recently for effectively transforming electrical energy to
mechanical work. Their large strains and conformability make them enticing materials which can be applied in many
domains: biomimetics, aerospace, mechanics, medicals, etc. In order to maximize actuator performance, the dielectric
elastomer actuators should have a high dielectric constant and high dielectric breakdown strength. Here we have
investigated the increase in permittivity of a commercial silicone elastomer by the addition of carbon nanotube. The
percolation threshold of the composites is obtained to be low. Experimental results suggest that for the case of
conductive filler particle-elastomer matrix interaction, actuation strain increases with increasing carbon nanotube content.
Dielectric elastomers (DE) are the most promising electroactive polymer materials capable of being applied in smart actuators. When the DE film sandwiched between two compliant electrodes is applied high electric field, due to the electrostatic force between two electrodes, the film expands in-plane and contracts out-of-plane such that its thickness becomes thinner. The thinner thickness results in higher electric field which inversely squeezes the film again. This positive feedback induces a mode of instability, known as electromechanical instability or pull-in instability. When the electric field exceeds certain critical value, the DE film collapses. In this paper, the elastic strain energy function with two material constants is applied to analyze the stability of dielectric elastomers, which facilitates to understand fully Suo's nonlinear theory. The results verify again the truth of this theory and exploit larger application spectrum. The method is capable of analyzing the stability of different dielectric materials with different values of k and the result can be useful on design of the dielectric elastomer actuator.
Dielectric elastomers (DEs) are one particular type of electroactive polymers. The excellent features of merit possessed
by dielectric elastomers make them the most performing materials which can be applied in many domains: biomimetics,
aerospace, mechanics, medicals, etc. In order to maximize actuator performance, the dielectric elastomer actuators
should have a high dielectric constant and high dielectric breakdown strength. In this paper, multi-walled carbon
nanotube (MWNT) is used to develop a particulate composite based on silicone elastomer matrix, with dielectric
permittivity improved. And the composite is designed to a new configuration of dielectric elastomer actuator to show
electrically activated linear contractions. Prototype samples of this folded actuator, along with the fabrication and
analysis is discussed here.
Dielectric elastomers (Des) are a type of EAPs with unique electrical properties and mechanical properties: high
actuation strains and stresses, fast response times, high efficiency, stability, reliability and durability. The excellent
figures of merit possessed by dielectric elastomers make them the most performing materials which can be applied in
many domains: biomimetics, aerospace, mechanics, medicals, etc. In this paper, we present a kind of electroactive
polymer composites based on silicone Dielectric elastomers with a high dielectric constant. Novel high DEs could be
realized by means of a composite approach. By filling an ordinary elastomer (e.g. silicone) with a component of
functional ceramic filler having a greater dielectric permittivity, it is possible to obtain a resulting composite showing
the fruitful combination of the matrix's advantageous elasticity and the filler's high permittivity. Here we add the
ferroelectric relaxor ceramics (mainly BaTiO3) which has high dielectric constant (>3000) to the conventional silicone
Dielectric elastomers, to get the dielectric elastomer which can exhibit high elastic energy densities induced by an
electric field of about 15 MV/m. Tests of the physical and chemical properties of the dielectric elastomers are conducted,
which verify our supposes and offer the experimental data supporting further researches.
Bio-mimetic actuators are inspired to the human or animal organ and they are aimed at replicating actions exerted by the
main organic muscles. We present here an inflated dielectric Electroactive Polymer actuator based on acrylic elastomer
aiming at mimicing the ocular muscular of the human eye. Two sheets of polyacrylic elastomer coated with conductive
carbon grease are sticked to a rotatable backbone, which function like an agonist-antagonist configuration. When
stimulating the two elastomer sheets separately, the rotatable
mid-arc of the actuator is capable of rotating from -50° to
50°. Experiments shows that the inflated actuator, compared with uninflated one, performs much bigger rotating angle
and more strengthened. Connected with the actuator via an elastic tensive line, the eyeball rotates around the
symmetrical axes. The realization of more accurate movements and emotional expressions of our native eye system is the
next step of our research and still under studied. This inflated dielectric elastomer actuator shows as well great potential
application in robofish and adaptive stucture.