A constitutive law for dielectric elastomers subject to high levels of stretch during combined electrostatic and mechanical loading: Elastomer stiffening and deformation dependent dielectric permittivity

Jiménez, Salomón M.A.; McMeeking, Robert M.

doi:10.1016/j.ijnonlinmec.2016.10.004

Cited by 23 publications

(23 citation statements)

References 38 publications

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“…A deformation-dependent permittivity was used by Jiménez & McMeeking [41,42] to examine the stability of thin film actuators coated with flexible electrodes and subject to in-plane equibiaxial stretch. They showed that, for an increase and subsequent decrease of the applied potential, hysteresis loops are generated in the charge and the in-plane stretch considered as functions of the electric potential.…”

Section: (A) Internal Stress Balancementioning

confidence: 99%

Instabilities of soft dielectrics

Dorfmann

Ogden

2019

Phil. Trans. R. Soc. A.

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The basic modern theory of nonlinear electroelasticity and its use in the formulation of constitutive laws governing the behaviour of dielectric elastomer materials was summarized in a recent review article by Dorfmann & Ogden (Dorfmann & Ogden 2017 Proc. R. Soc. A 473 , 20170311 ( doi:10.1098/rspa.2017.0311 )). The theory is used, in particular, to analyse the behaviour of transducer devices such as actuators and sensors. Important considerations for the design and effective functioning of such devices are the issues of material and geometric instabilities. Following on from the above-cited work, the present paper provides a detailed account of the types of instabilities that arise for some of the geometries used in transducer devices and the theory that is adopted for the analysis of such instabilities. The theory is then used in two illustrative examples: (i) determination of instabilities of a thin electroelastic plate with flexible electrodes attached to its major surfaces, in particular comparison of the results for the so-called Hessian approach and a general incremental bifurcation analysis in respect of an equibiaxially stretched plate, with numerical results presented for a Gent electroelastic model; (ii) a general analysis of axi-symmetric bifurcation from a circular cylindrical configuration of a thin-walled tube of an electroelastic material with flexible electrodes on its curved surfaces, illustrated by numerical results for neo-Hookean and Gent electroelastic models. This article is part of the theme issue ‘Rivlin's legacy in continuum mechanics and applied mathematics’.

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Section: (A) Internal Stress Balancementioning

confidence: 99%

Instabilities of soft dielectrics

Dorfmann

Ogden

2019

Phil. Trans. R. Soc. A.

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“…Rubber materials are usually subject to periodic mechanical and electrical forces, e.g., in tires and insulators. Interest in the shape changes induced by electric fields [1][2][3][4] has grown recently, driven by different applications. For instance, dielectric elastomer actuators (DEAs) [5] display intriguing attributes similar to biological muscles, including self-sensing abilities [6,7] and improving the intelligence of gripping technologies [8].…”

Section: Introductionmentioning

confidence: 99%

Rubber Surface Change and Static Charging under Periodic Stress

Santos

Campo

Silva

et al. 2018

Colloids and Interfaces

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Rubber materials play an important role in robotics, due to their sensing and actuating abilities, that are exploited in soft smart materials endowed with shape-adaptive and electroadhesive properties. The application of an electric field produces non-linear deformation that has been extensively modelled, but is not understood at the molecular level. The symmetric effect (the production of an electric field due to rubber deformation) was recently discovered and explained as follows: rubber surface chemical composition and adsorptive properties change during rubber deformation, allowing the surface to exchange charge with the atmosphere. The present work describes the complex surface morphology and microchemistry of tubing made from vulcanized natural rubber, showing that it is rough and made from two domain types: stiffer elevations containing Br or Al (depending on the sample used) and O, that rise above an elastic base that is exempt of elements other than C and H. The surface area fraction occupied by the elastic base is higher in the strained rubber than when it is relaxed. Electrostatic potential on rubber surfaces was measured as a function of the stretching frequency, using Kelvin electrodes and showing frequency-dependent potential variation. This is explained considering charge exchange between the atmosphere and rubber surface, mediated by water vapor adsorbed in the stretched rubber and trapped when it relaxes.Colloids Interfaces 2018, 2, 55 2 of 11 of rubber performance in many important situations, but this does not benefit from knowledge on the molecular mechanisms of the observed phenomena.Recent work from this group described a new finding on the electrostatic behavior of elastomers: in short, rubber tube stretching, followed by relaxation, provokes the appearance of transient excess charge that is more pronounced under higher relative humidity [14]. This effect is not related to any existing electrostatic charging phenomenon (piezoelectricity, flexoelectricity, triboelectricity, and contact charging) and a new mechanism was then proposed to explain charge pick-up and dissipation by stretched elastomers, as the result of water adsorption and the partition of water ions (H + and OH − ) in the rubber-air interface, due to periodic rubber surface modification.Other unexpected findings on electrostatic phenomena in dielectrics have been described recently, leading to a revision of widespread ideas on electrostatic charging and its mechanisms [15]. Important aspects of electrostatic phenomena are not well understood [16][17][18], but tribo-and piezoelectricity are important sources of the electrostatic potentials detected in anthropic environments, often reaching many-thousand volts. They are currently used in nanotribogenerators, with great success. This is creating new opportunities for energy scavenging [19][20][21], and it is probably relevant to the prevention of harmful electrostatic discharge.Knowledge of the electrostatic behavior of elastomers is more limited than in the case of semicrystallin...

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“…From microlevel, dipole moment of a water molecule in tissue differs from that of an isolated one [37]. This is mainly because water molecule in tissue is further polarized by effect by its nearby neighbors and the biomolecules [38,39]. The blood volume fraction is unstable as the frequency changes as in Figures 2 and 3.…”

Section: Comparison Of Theory and Experimentsmentioning

confidence: 97%

Effective Permittivity of Biological Tissue: Comparison of Theoretical Model and Experiment

Ning

Zhang

2017

Mathematical Problems in Engineering

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Permittivity of biological tissue is a critical issue for studying the biological effects of electromagnetic fields. Many theories and experiments were performed to measure or explain the permittivity characteristics in biological tissue. In this paper, we investigate the permittivity parameter in biological tissues via theoretical and experimental analysis. Firstly, we analyze the permittivity characteristic in tissue by using theories on composite material. Secondly, typical biological tissues, such as blood, fat, liver, and brain, are measured by HP4275A Multi-Frequency LCR Meter within 10 kHz to 10 MHz. Thirdly, experimental results are compared with the Bottcher-Bordewijk model, the Skipetrov equation, and the Maxwell-Gannett theory. From the theoretical perspective, blood and fat are regarded as the composition of liver and brain because of the high permittivity in blood and the opposite in fat. Volume fraction of blood in liver and brain is analyzed theoretically, and the applicability and the limitation of the models are also discussed. These results benefit further study on local biological effects of electromagnetic fields.

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A constitutive law for dielectric elastomers subject to high levels of stretch during combined electrostatic and mechanical loading: Elastomer stiffening and deformation dependent dielectric permittivity

Cited by 23 publications

References 38 publications

Instabilities of soft dielectrics

Instabilities of soft dielectrics

Rubber Surface Change and Static Charging under Periodic Stress

Effective Permittivity of Biological Tissue: Comparison of Theoretical Model and Experiment

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