Academic literature on the topic 'Dielectric Hyperelastic Structures'
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Journal articles on the topic "Dielectric Hyperelastic Structures"
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Lai, Heather L., and Chin An Tan. "Modeling the constraint effects of compliant electrodes in dielectric elastomers under uniaxial loading." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 230, no. 15 (August 9, 2016): 2623–36. http://dx.doi.org/10.1177/0954406215602035.
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Dielectric elastomers are composite thin film structures composed of a dielectric polymer between compliant electrodes. Previous hyperelastic models have not modeled the constraint effects of compliant electrodes on the lateral contraction of the dielectric material as it stretches, and are therefore unable to fully describe the electromechanical behavior of the dielectric elastomer or provide a means to understand the constraint effects. An empirical boundary coefficient is introduced to model these constraint effects on the lateral boundaries of the material under uniaxial tension. Employing an averaged stretch ratio concept, it is shown that this coefficient can be obtained from experimentally measurable geometric variables. Values for the boundary coefficients of sample dielectric elastomer films were obtained from experiments performed on a uniaxial test stand. Incorporating the boundary coefficient into the model formulation, a specific hyperelastic stress–strain relation is derived to describe the electromechanical behavior of dielectric elastomers under combined uniaxial tension and electrical loading. Comparison of the experimental and predicted values of the induced force in the axial direction due to the Maxwell stress based on the uniaxial model shows favorable agreement.
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Khurana, Aman, Atul Kumar Sharma, and M. M. Joglekar. "Nonlinear oscillations of electrically driven aniso-visco-hyperelastic dielectric elastomer minimum energy structures." Nonlinear Dynamics 104, no. 3 (April 8, 2021): 1991–2013. http://dx.doi.org/10.1007/s11071-021-06392-5.
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Kashyap, Kartik, Atul Kumar Sharma, and M. M. Joglekar. "Nonlinear dynamic analysis of aniso-visco-hyperelastic dielectric elastomer actuators." Smart Materials and Structures 29, no. 5 (March 31, 2020): 055014. http://dx.doi.org/10.1088/1361-665x/ab7a3c.
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Lochmatter, Patrick, Gabor Kovacs, and Michael Wissler. "Characterization of dielectric elastomer actuators based on a visco-hyperelastic film model." Smart Materials and Structures 16, no. 2 (February 20, 2007): 477–86. http://dx.doi.org/10.1088/0964-1726/16/2/028.
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Alibakhshi, Amin, Shahriar Dastjerdi, Bekir Akgöz, and Ömer Civalek. "Parametric vibration of a dielectric elastomer microbeam resonator based on a hyperelastic cosserat continuum model." Composite Structures 287 (May 2022): 115386. http://dx.doi.org/10.1016/j.compstruct.2022.115386.
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Chang, Mengzhou, Zhenqing Wang, Liyong Tong, and Wenyan Liang. "Effect of geometric size on mechanical properties of dielectric elastomers based on an improved visco-hyperelastic film model." Smart Materials and Structures 26, no. 3 (February 13, 2017): 035033. http://dx.doi.org/10.1088/1361-665x/aa5491.
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Xiang, Junxiang, Jiaojiao Guo, Bo Li, Yingwei Li, Linhui Ouyang, Langquan Shui, and Ze Liu. "Arbitrarily Patterned Active Wrinkles in Highly Stretched Substrate-Free Dielectric Elastic Membrane." Journal of Applied Mechanics 88, no. 2 (November 3, 2020). http://dx.doi.org/10.1115/1.4048803.
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Abstract Dynamic wrinkle patterns provide an effective approach for on-demand tuning of membrane optical and mechanical properties to realize a smart membrane. Related applications depend on forming and controlling of a sophisticated wrinkling region. Herein, by using strip-structured electrode couples, we enable regular and ordered wrinkling patterns in an arbitrarily shaped region in a pre-stretched substrate-free dielectric elastic membrane. By considering the electromechanical coupling in a substrate-free hyperelastic membrane, the winkling condition and wavelength are predicated theoretically. Supported by the theoretical results, a series of experimental and numerical demonstrations are realized. The method proposed in this work provides a general framework for forming controllable highly ordered wrinkling patterns in a complex/large area of a substrate-free membrane, which could provide useful guidance for the application of dielectric elastomers in intelligent materials and structures.
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Khajamoinuddin, Shaikbepari Mohmmed, Aritra Chatterjee, MR Bhat, Dineshkumar Harursampath, and Namrata Gundiah. "Mechanical characterization of a woven multi-layered hyperelastic composite laminate under uniaxial loading." Journal of Composite Materials, April 20, 2021, 002199832110115. http://dx.doi.org/10.1177/00219983211011528.
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We characterize the material properties of a woven, multi-layered, hyperelastic composite that is useful as an envelope material for high-altitude stratospheric airships and in the design of other large structures. The composite was fabricated by sandwiching a polyaramid Nomex® core, with good tensile strength, between polyimide Kapton® films with high dielectric constant, and cured with epoxy using a vacuum bagging technique. Uniaxial mechanical tests were used to stretch the individual materials and the composite to failure in the longitudinal and transverse directions respectively. The experimental data for Kapton® were fit to a five-parameter Yeoh form of nonlinear, hyperelastic and isotropic constitutive model. Image analysis of the Nomex® sheets, obtained using scanning electron microscopy, demonstrate two families of symmetrically oriented fibers at 69.3°± 7.4° and 129°± 5.3°. Stress-strain results for Nomex® were fit to a nonlinear and orthotropic Holzapfel-Gasser-Ogden (HGO) hyperelastic model with two fiber families. We used a linear decomposition of the strain energy function for the composite, based on the individual strain energy functions for Kapton® and Nomex®, obtained using experimental results. A rule of mixtures approach, using volume fractions of individual constituents present in the composite during specimen fabrication, was used to formulate the strain energy function for the composite. Model results for the composite were in good agreement with experimental stress-strain data. Constitutive properties for woven composite materials, combining nonlinear elastic properties within a composite materials framework, are required in the design of laminated pretensioned structures for civil engineering and in aerospace applications.
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Pahari, Basanta, Eugenia Stanisauskis, Somayeh Mashayekhi, and William S. Oates. "An Entropy Dynamics Approach for Deriving and Applying Fractal and Fractional Order Viscoelasticity to Elastomers." Journal of Applied Mechanics, April 21, 2023, 1–17. http://dx.doi.org/10.1115/1.4062389.
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Abstract Entropy dynamics is a Bayesian inference methodology that can be used to quantify time-dependent posterior probability densities that guide development of complex material models using information theory. Here we expand its application to non-Gaussian processes to evaluate how fractal structure can influence fractional hyperelasticity and viscoelasticity in elastomers. We investigate how kinematic constraints on fractal polymer network deformation influences the form of hyperelastic constitutive behavior and viscoelasticity in soft materials such as dielectric elastomers which have applications in the development of adaptive structures. The modeling framework is validated on two dielectric elastomers, VHB 4910 and 4949, over a broad range of stretch rates. It is shown that local fractal time derivatives are equally effective at predicting viscoelasticity in these materials in comparison to non-local fractional time derivatives under constant stretch rates. We describe the origin of this accuracy which has implications for simulating larger scale problems such as finite element analysis given the differences in computational efficiency of non-local fractional derivatives versus local fractal derivatives.
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Zhao, Yunhua, and Li Wen. "Dynamic modeling with quantifying dissipated power density and experimental validation of dielectric elastomer actuators." Smart Materials and Structures, March 28, 2023. http://dx.doi.org/10.1088/1361-665x/acc825.
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Abstract This paper proposes a dynamic electromechanical model for dielectric elastomer actuators (DEAs) with dissipative processes. Dielectric loss of elastomers, resistance of electrodes, actuator geometry, elastomer viscoelasticity and nonlinear electromechanical coupling are considered, and a new visco-hyperelastic constitutive model with frequency-dependent parameters is developed for large-strain elastomers. The dynamic responses of DEAs at different driving frequencies are experimentally measured and comprehensively compared with those predicted results. The relative errors over the time period of 0-50s at 5 Hz and 7 Hz are respectively 3.6% and 3.4%, demonstrating the effectiveness of the model. The proposed dynamic model can not only predict the frequency response of DEAs but also characterize the creep and hysteresis behavior with reasonable accuracy. The power density dissipated during dielectric elastomer actuation is calculated and analyzed. The results suggest that selecting low-resistance electrodes and elastomers with short dielectric relaxation time and low viscous loss is a feasible way to achieve high energy conversion efficiency for DEAs. This work can be helpful for the design and control of DEAs, paving the way for their practical applications.
Dissertations / Theses on the topic "Dielectric Hyperelastic Structures"
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Burela, Ramesh Gupta. "Asymptotically Correct Dimensional Reduction of Nonlinear Material Models." Thesis, 2011. https://etd.iisc.ac.in/handle/2005/3996.
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This work aims at dimensional reduction of nonlinear material models in an asymptotically accurate manner. The three-dimensional(3-D) nonlinear material models considered include isotropic, orthotropic and dielectric compressible hyperelastic material models. Hyperelastic materials have potential applications in space-based inflatable structures, pneumatic membranes, replacements for soft biological tissues, prosthetic devices, compliant robots, high-altitude airships and artificial blood pumps, to name a few. Such structures have special engineering properties like high strength-to-mass ratio, low deflated volume and low inflated density. The majority of these applications imply a thin shell form-factor, rendering the problem geometrically nonlinear as well. Despite their superior engineering properties and potential uses, there are no proper analysis tools available to analyze these structures accurately yet efficiently. The development of a unified analytical model for both material and geometric nonlinearities encounters mathematical difficulties in the theory but its results have considerable scope. Therefore, a novel tool is needed to dimensionally reduce these nonlinear material models.
In this thesis, Prof. Berdichevsky’s Variational Asymptotic Method(VAM) has been applied rigorously to alleviate the difficulties faced in modeling thin shell structures(made of such nonlinear materials for the first time in the history of VAM) which inherently exhibit geometric small parameters(such as the ratio of thickness to shortest wavelength of the deformation along the shell reference surface) and physical small parameters(such as moderate strains in certain applications).
Saint Venant-Kirchhoff and neo-Hookean 3-D strain energy functions are considered for isotropic hyperelastic material modeling. Further, these two material models are augmented with electromechanical coupling term through Maxwell stress tensor for dielectric hyperelastic material modeling. A polyconvex 3-D strain energy function is used for the orthotropic hyperelastic model. Upon the application of VAM, in each of the above cases, the original 3-D nonlinear electroelastic problem splits into a nonlinear one-dimensional (1-D) through-the-thickness analysis and a nonlinear two-dimensional(2-D) shell analysis. This greatly reduces the computational cost compared to a full 3-D analysis. Through-the-thickness analysis provides a 2-D nonlinear constitutive law for the shell equations and a set of recovery relations that expresses the 3-D field variables (displacements, strains and stresses) through thethicknessintermsof2-D shell variables calculated in the shell analysis (2-D).
Analytical expressions (asymptotically accurate) are derived for stiffness, strains, stresses and 3-D warping field for all three material types. Consistent with the three types of 2-D nonlinear constitutive laws,2-D shell theories and corresponding finite element programs have been developed.
Validation of present theory is carried out with a few standard test cases for isotropic hyperelastic material model. For two additional test cases, 3-Dfinite element analysis results for isotropic hyperelastic material model are provided as further proofs of the simultaneous accuracy and computational efficiency of the current asymptotically-correct dimensionally-reduced approach. Application of the dimensionally-reduced dielectric hyperelastic material model is demonstrated through the actuation of a clamped membrane subjected to an electric field. Finally, the through-the-thickness and shell analysis procedures are outlined for the orthotropic nonlinear material model.
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Burela, Ramesh Gupta. "Asymptotically Correct Dimensional Reduction of Nonlinear Material Models." Thesis, 2011. http://etd.iisc.ernet.in/2005/3909.
Full textAbstract:
This work aims at dimensional reduction of nonlinear material models in an asymptotically accurate manner. The three-dimensional(3-D) nonlinear material models considered include isotropic, orthotropic and dielectric compressible hyperelastic material models. Hyperelastic materials have potential applications in space-based inflatable structures, pneumatic membranes, replacements for soft biological tissues, prosthetic devices, compliant robots, high-altitude airships and artificial blood pumps, to name a few. Such structures have special engineering properties like high strength-to-mass ratio, low deflated volume and low inflated density. The majority of these applications imply a thin shell form-factor, rendering the problem geometrically nonlinear as well. Despite their superior engineering properties and potential uses, there are no proper analysis tools available to analyze these structures accurately yet efficiently. The development of a unified analytical model for both material and geometric nonlinearities encounters mathematical difficulties in the theory but its results have considerable scope. Therefore, a novel tool is needed to dimensionally reduce these nonlinear material models.
In this thesis, Prof. Berdichevsky’s Variational Asymptotic Method(VAM) has been applied rigorously to alleviate the difficulties faced in modeling thin shell structures(made of such nonlinear materials for the first time in the history of VAM) which inherently exhibit geometric small parameters(such as the ratio of thickness to shortest wavelength of the deformation along the shell reference surface) and physical small parameters(such as moderate strains in certain applications).
Saint Venant-Kirchhoff and neo-Hookean 3-D strain energy functions are considered for isotropic hyperelastic material modeling. Further, these two material models are augmented with electromechanical coupling term through Maxwell stress tensor for dielectric hyperelastic material modeling. A polyconvex 3-D strain energy function is used for the orthotropic hyperelastic model. Upon the application of VAM, in each of the above cases, the original 3-D nonlinear electroelastic problem splits into a nonlinear one-dimensional (1-D) through-the-thickness analysis and a nonlinear two-dimensional(2-D) shell analysis. This greatly reduces the computational cost compared to a full 3-D analysis. Through-the-thickness analysis provides a 2-D nonlinear constitutive law for the shell equations and a set of recovery relations that expresses the 3-D field variables (displacements, strains and stresses) through thethicknessintermsof2-D shell variables calculated in the shell analysis (2-D).
Analytical expressions (asymptotically accurate) are derived for stiffness, strains, stresses and 3-D warping field for all three material types. Consistent with the three types of 2-D nonlinear constitutive laws,2-D shell theories and corresponding finite element programs have been developed.
Validation of present theory is carried out with a few standard test cases for isotropic hyperelastic material model. For two additional test cases, 3-Dfinite element analysis results for isotropic hyperelastic material model are provided as further proofs of the simultaneous accuracy and computational efficiency of the current asymptotically-correct dimensionally-reduced approach. Application of the dimensionally-reduced dielectric hyperelastic material model is demonstrated through the actuation of a clamped membrane subjected to an electric field. Finally, the through-the-thickness and shell analysis procedures are outlined for the orthotropic nonlinear material model.
Book chapters on the topic "Dielectric Hyperelastic Structures"
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Alibakhshi, Amin, Shahriar Dastjerdi, Mohammad Malikan, and Victor A. Eremeyev. "A Review of Hyperelastic Constitutive Models for Dielectric Elastomers." In Advanced Structured Materials, 1–17. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-22093-7_1.
Full textConference papers on the topic "Dielectric Hyperelastic Structures"
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Fadodun, O. O. "Finite electroelastic deformation of dielectric semilinear hyperelastic tubes." In Advanced Topics in Mechanics of Materials, Structures and Construction. Materials Research Forum LLC, 2023. http://dx.doi.org/10.21741/9781644902592-35.
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Abstract. This study examines the finite electroelastic deformation problem of extension and inflation coupling of dielectric semilinear hyperelastic tubes with closed ends under the influence of internal pressure, axial loads and radial electric field. The laws of thermodynamics and Coleman-Noll procedure are used to derive the electroelastic constitutive model of the tube. The solution of the consequent electromechanical field equations shows that the applied radial electric field associated with the equal and opposite charges on the electrode coated surfaces contributes to both internal pressure and axial loads of the closed tube. Furthermore, it is obtained that the stress propagation in dielectric semilinear hyperelastic solids is sensitive to the electric displacement field generated within the solids while the accompanying electric field interacts with the deformation of the solids. Finally, and among other things, the graphical illustration shows that the radial electric field generated within the tube increases with the increasing azimuthal stretch.
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Miles, Paul, Michael Hays, Ralph Smith, and William S. Oates. "Uncertainty Analysis of a Finite Deformation Viscoelastic Model." In ASME 2014 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/smasis2014-7440.
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The viscoelasticity of the dielectric elastomer, VHB 4910, is experimentally characterized, modeled, and analyzed using uncertainty quantification. These materials are known for their large field induced deformation and applications in smart structures, although the rate dependent viscoelastic effects are not well understood. To address this issue, we first quantify hyperelastic and viscoelastic model uncertainty by comparing a finite deformation viscoelastic model to uni-axial rate dependent experiments. The utilization of Bayesian statistics is shown to provide additional insight into different viscoelastic processes within elastomers. This is demonstrated by coupling two hyperelastic models, an Ogden model and a nonaffine model, to different types of viscoelastic models.
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Berselli, Giovanni, Rocco Vertechy, Mitja Babič, and Vincenzo Parenti Castelli. "Implementation of a Variable Stiffness Actuator Based on Dielectric Elastomers: A Feasibility Study." In ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/smasis2012-8144.
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Dielectric Elastomers (DE) seem to be a promising technology for the implementation of light and compact Variable Stiffness Actuators (VSAs), thanks to their large power densities, low costs and shock-insensitivity. Nonetheless, the development of DE-based VSA is not trivial owing to the relevant dissipative phenomena that affect the DE when subjected to rapidly changing deformations. In this context, the purpose of the present paper is to investigate the practical feasibility of DE-based VSA. As a case study, two conically-shaped actuators, in agonistic-antagonistic configuration, are modeled accounting for the visco-hyperelastic nature of the DE films. The model is then linearized and employed for the design of a stiffness controller. The control algorithm requires the knowledge of the actuator configuration (via a position sensor) and of the force exchanged with the environment (via a force sensor). An optimum full-state observer is then implemented, which enables both accurate estimation of the DE time-dependent behavior and adequate suppression of sensor measurement noise. At last, experimental results are provided together with the description of an effective electronic driver that allows an independent activation of the agonistic-antagonistic DE membranes.
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Soulimane, Sofiane, Wen-Pin Shih, Marc Vedrenne, and Henri Camon. "Ceramic Siloxane Composite as a Future Elastomer Dielectric for Micro-Actuator Realization." In ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/smasis2012-8085.
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Polymer materials have been proposed to be good candidates for the development of new actuators. Due to their tunable mechanical and electrical properties, they can be used as electro-active devices. In this contribution, we focus on dielectric elastomers based actuators, and word toward establishing innovative and alternative integration/miniaturization processes inspired from microelectronics and MEMS technology. Dielectric elastomer actuators are made of an elastomer dielectric layer sandwiched between two conductive electrodes. Upon voltage application attraction forces between the electrodes generates a mechanical displacement correlated with the elastomer Young modulus and permittivity. Here, we propose to use the polydimethylesiloxane (PDMS) due to its high elasticity and its permittivity made adjustable by addition of ceramic nanoparticles. An original process for structuring PDMS layers is developed to overcome the technological challenges encountered during the integration of such materials in a micro-actuator. In this paper, we present several results of characterization that allowed us to better understand the physicochemical mechanisms involved at different technological steps for both the material alone or mixed with Titanate of Barium (TiO3Ba) nanoparticles. We also measured the permittivity and the elasticity modulus of these materials at the end of the manufacturing process thereby verifying the conservation and the enhancement of the initial properties that set our choice. These results are very promising for increasing the electrostatic pressure or to lower the actuation voltage. To make a prediction of permittivity by a mixing rule, we inspect some theories in this aim. Finally, we demonstrate that the actuation response of charged elastomer with TiO3Ba nanoparticles follows a hyperelastic behavior. This result is particularly helpful for the design of a micro-actuator in a given application.
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Li, Tiefeng, Christoph Keplinger, Liwu Liu, Richard Baumgartner, and Shaoxing Qu. "Modeling of Inhomogeneous Deformation in a Dielectric Elastomer Generator for Energy Harvesting." In ASME 2010 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2010. http://dx.doi.org/10.1115/smasis2010-3792.
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Dielectric elastomer transducers promise to combine high energy density at low cost and lightweight when used as actuators or for energy harvesting generators. A cornucopia of possible applications have been demonstrated over the last years including soft matter based actuators for robotics, tunable optics, medical devices, space robotics and energy harvesters. Prestretch effects and the electromechanical instability have been shown to highly influence the performance of dielectric elastomer transducers. Nevertheless only sparse research has been done on instability and prestretch effects of dielectric elastomer membranes under inhomogeneous deformation. Dielectric elastomer transducers consist of an elastomer membrane sandwiched between a pair of compliant electrodes and can be considered as deformable capacitors with variable capacitance. Here we focus on a specific experimental setup well suited to study the performance of dielectric elastomer materials for energy harvesting. In this setup an elastomer membrane is equibiaxially prestretched and fixed on top of an air chamber which is connected to a compressed air reservoir, the source of mechanical energy for thegenerator. From the electrical point of view the compliant electrodes on the elastomer membrane can be connected to both a high and low voltage charge reservoir. Thus the change in capacitance during deformation can be used to boost charges from the low voltage reservoir to the high voltage reservoir. Experimentally, different constant voltages are applied to the elastomer membrane during inflation and the air chamber pressure is recorded together with the shape and the volume of the balloon for different initial prestretches. The usual instability in the pressure-volume curves of ballon inflation experiments are shown to be influenced by applied voltage and prestretch. Theoretically, the setup is modeled as a thermodynamic system, with static electric and mechanical load where quasi-static equilibrium states can be achieved. To describe the inhomogeneous deformation and to correctly account for the hyperelastic behavior of the material over the whole deformation range an asymmetric model is built based on the Arruda-Boyce material model. The results of the numerical simulation are fitted to the experimental data to obtain significant material parameters in order to predict the optimal operation regime of the dielectric elastomer generator. The experimental results accompanied by the theoretical analysis may be used as a benchmark for the applicability of dielectric elastomer generators and pave ways for understanding the dielectric elastomer behavior under inhomogeneous deformation.
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Berselli, Giovanni, Rocco Vertechy, Marco Fontana, and Marcello Pellicciari. "An Experimental Assessment of the Thermo-Elastic Response in Acrylic Elastomers and Natural Rubbers for Application on Electroactive Polymer Transducers." In ASME 2014 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/smasis2014-7604.
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Dielectric Elastomers (DEs) are deformable dielectrics, which are currently used as active materials in mechatronic transducers, such as actuators, sensors and generators. Nonetheless, at the present state of the art, the industrial exploitation of DE-based devices is still hampered by the irregular electro-mechanical behavior of the employed materials, also due to the unpredictable effects of environmental changes in real world applications. In many cases, DE transducers are still developed via trial-and-error procedures rather than through a well-structured design practice, one reason being the lack of experimental data along with reliable constitutive parameters of many potential DE materials. Therefore, in order to provide the practicing engineer with some essential information, an open-access database for DE materials has been recently created and presented in [1]. Following the same direction, this paper addresses the temperature effect on the visco-hyperelastic behavior of two DE candidates, namely a natural rubber (ZRUNEK A1040) and a well-known acrylic elastomer (3M VHB 4905). Measurements are performed on pure shear specimens placed in a climactic chamber. Experimental stress-strain curves are then provided, which makes it possible to predict hyperelasticity, plasticity, viscosity, and Mullins effect as function of the environmental temperature. Properties of these commercial elastomeric membranes are finally entered in the database and made available to the research community.
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Cooley, Christopher G., and Robert L. Lowe. "Non-Linear Vibration of Thick Dielectric Membrane Disks With Radial Loads." In ASME 2020 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/smasis2020-2326.
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Abstract This study analyzes the large-amplitude, non-linear vibration of dielectric elastomer membrane disks with applied voltages through their thickness and mechanical loads applied radially around their outer circumferential surface. The material is modeled as an isotropic ideal dielectric, with the large-stretch mechanical stiffening captured using the Gent hyperelastic constitutive model. The fully non-linear equation of motion for the coupled electromechanical system is derived using Hamilton’s principle. The disk comes to a steady equilibrium where the compressive stresses due to the applied voltage balance the tensile stresses from the applied radial loads. The equilibria are calculated numerically for a wide range of radial loads, applied voltages, and limiting stretches. It is possible for the disk to have two stable steady equilibria at given radial load and applied voltage, which gives rise to an instability where extreme stretches occur for infinitesimal changes in applied voltage. The equation of motion is determined for small vibrations of the system about equilibrium. Unlike for thin membrane disks, the vibrating mass of thick membrane disks depends on the steady equilibrium stretch. The natural frequency for membrane disks meaningfully decreases with increasing thickness due to the inertia associated with dynamic changes in the membrane thickness. The amount of axial inertia depends on the ratio of the nominal disk thickness to its radius and the steady equilibrium stretch. Large amplitude vibrations are numerically investigated for a wide range of system parameters. The frequency response characteristics of circular membranes due to sinusoidal voltage fluctuations are analyzed about small and large equilibrium stretches. Whereas axial inertia meaningfully alters the frequency response about small equilibrium stretches, it has negligible effects on the frequency response about large equilibrium stretches.
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Erol, Anil, Saad Ahmed, Paris von Lockette, and Zoubeida Ounaies. "Analysis of Microstructure-Based Network Models for the Nonlinear Electrostriction Modeling of Electro-Active Polymers." In ASME 2017 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/smasis2017-3979.
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Relaxor ferroelectric polymers are a unique branch of electro-active polymers (EAPs) that generate high electromechanical strain with relatively low hysteresis and high nonlinearity. Polyvinylidene fluoride-based EAPs possess these qualities due to the semicrystalline nature of their microstructure. The interactions of electric dipoles within the microstructure of the material generate large strains under an external electric field, and the reduced crystalline domain sizes yield a relaxor effect by exhibiting low hysteresis and hyperelastic properties. This phenomenon has been partially modeled by previous works, but micro-electro-mechanisms for electrostriction in the microstructure have been largely ignored. This study focuses on the effects of various microstructural frameworks on the nonlinear dielectric behavior of dipole-based, semicrystalline EAPs. The Helmholtz free energy function of a microscopic representative volume element (RVE) is composed of an electrostatic energy and an elastic energy. The dipole-dipole interaction energy is prescribed for the electrostatic forces observed among the crystalline regions, and the elastic component attributed to the relaxation of the amorphous phase is modeled by the hyperelastic eight-chain model, which is microstructure-based. The RVE of the system is modeled by a central dipole surrounded by dipoles whose relative spatial locations are determined by a probability distribution function (PDF). The hyperelastic amorphous phase constitutes the volume separating the central and surrounding dipoles. The free energy of the RVE is implemented into a continuum description of the equilibrium of the system to obtain electromechanical relations. Additionally, this electromechanical response data is applied to a 1D structural mechanics model for simulating the large deformation of a multi-layered beam. The effects of microstructure on electrostrictive coupling are explored by varying the centers and deviations of dipole locations within the PDF. Discrete microstructural arrangements representing 3-chain network averaging schemes may be studied alongside more continuous ellipsoidal or random models of dipole spatial arrangements. The simulation results of the PDF-based networks are in good agreement with experimental data. The results indicate that the electrostrictive behavior of EAPs is strongly dependent on (1) the relative dipole spatial locations and (2) the extent of the regions containing dipoles, which represent crystalline domains. The model finds that adding extra crystalline domains in the network averaging schemes generates a better characteristic behavior due to a broader averaging of spatial orientations. These results offer a gateway to predicting microstructurally-dependent dipole-based behavior that can lead to the predictive theoretical tailoring of microstructures for desired electromechanical properties.
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Erol, Anil, Sarah Masters, Paris von Lockette, and Zoubeida Ounaies. "On the Modeling and Experimental Validation of Multi-Field Polymer-Based Bimorphs." In ASME 2016 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/smasis2016-9178.
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Origami — the Japanese art of folding — has inspired various engineering applications for several decades due to its ability to manipulate complex shapes. In our study, multi-field actuated self-folding Origami structures are developed with the implementation of two classes of smart materials: relaxor ferroelectric polymers and magneto-active elastomers (MAEs). The chosen relaxor ferroelectric is P(VDF-TrFE-CTFE), a P(VDF)-based terpolymer and the MAE is a PDMS substrate with embedded barium hexaferrite particles. At the macroscale, this study involves the modeling of the large deformation of a bimorph comprising the aforementioned magnetically and electrically actuated materials using a 1D analytical model derived from the equilibrium of a differential element. The large deformation is extracted from curvatures solved at each point for the resulting differential equation of the equilibrium state. On the microscale, this study also considers the nonlinear behavior of the smart materials. The nonlinear dielectric response of the relaxor ferroelectric polymer is captured by an electric field-dependent electrostrictive coefficient derived from a microstructure-based energy balance for the electrostriction of the terpolymer. The energy density function is postulated to be composed of an elastic contribution described by the Arruda-Boyce hyperelastic model and an electric contribution based on dipole-dipole interactions. On the other hand, a magnetic field-dependent torque drives the actuation of the MAEs, which is also dependent on the orientation of the material to the field. The integration of the micro and macro components results in an analytical model of a 1D, multi-layered flat structure that can be numerically solved for displacements under combined fields. The model is compared with well-matching experimental results of a unimorph and a bimorph structure as validation. The experiments measured the tip displacement of the beam under combined fields for a quantitative analysis. The study takes the analysis further by optimizing parameters such as geometry, field strengths, and the combination of active layers for relevant target shapes.