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Journal ArticleDOI

Nonlinear and time-dependent electromechanical behavior of polyvinylidene fluoride

01 Jun 2006-Smart Materials and Structures (IOP Publishing)-Vol. 15, Iss: 3, pp 767-781
TL;DR: In this article, the results from electromechanical tests conducted on polyvinylidene fluoride (PVDF) sheets showing its nonlinear and time-dependent EM behavior are described.
Abstract: This paper describes the results from electromechanical tests conducted on polyvinylidene fluoride (PVDF) sheets showing its nonlinear and time-dependent electromechanical behavior. Mechanical and electromechanical tests were carried out for both uniaxially stretched and biaxially stretched PVDF sheets. The tests show nonlinearity in both the stress–strain response and the time-dependent response. Electromechanical dynamic tests were conducted at various superimposed pre-stress conditions. From the dynamical electromechanical tests, it is found that both biaxially stretched and uniaxially stretched PVDF sheets exhibit pre-stress dependence of their electromechanical coefficients. In addition, an attempt has been made to model the mechanical and the electromechanical behavior using a simple three-parameter viscoelastic solid model. The model captures the trends observed in the experiments and is recommended as a useful tool for designs using these materials.
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30 Dec 2013
TL;DR: In this article, the authors focus on smart materials, structures and systems, which are also referred to as intelligent, adaptive, active, sensory and metamorphic, and the purpose of these materials from the perspective of smart systems is their ability to minimize life-cycle cost and/or expand the performance envelope.
Abstract: The twenty-first century could be called the 'Multifunctional Materials Age' The inspiration for multifunctional materials comes from nature, and therefore these are often referred to as bio-inspired materials Bio-inspired materials encompass smart materials and structures, multifunctional materials and nano-structured materials This is a dawn of revolutionary materials that may provide a 'quantum jump' in performance and multi-capability This book focuses on smart materials, structures and systems, which are also referred to as intelligent, adaptive, active, sensory and metamorphic The purpose of these materials from the perspective of smart systems is their ability to minimize life-cycle cost and/or expand the performance envelope The ultimate goal is to develop biologically inspired multifunctional materials with the capability to adapt their structural characteristics (such as stiffness, damping and viscosity) as required, monitor their health condition, perform self-diagnosis and self-repair, morph their shape and undergo significant controlled motion over a wide range of operating conditions

72 citations

Journal ArticleDOI
TL;DR: In this paper, an effective strategy based on the nonlinear elasticity theory is proposed to model the mechanical output of a trilayer conjugated polymer beam under actuation.
Abstract: Conjugated polymers are promising actuation materials for biomimetic robots and biomedical devices. Large bending is involved in some of these applications. This poses significant challenges in electromechanical modeling, because the linear elasticity theory is only valid when the strain is small. In this paper an effective strategy based on the nonlinear elasticity theory is proposed to model the mechanical output of a trilayer conjugated polymer beam under actuation. Instead of using the elastic modulus as in the linear elasticity theory, we use a nonlinear strain energy function to capture the stored elastic energy under actuation-induced swelling, which further allows us to compute the induced stress. The deformation variables are obtained by numerically solving the force and bending moment balance equations simultaneously. Experimental results have demonstrated that the proposed model shows superiority over the linear model, and is able to capture the actuation behavior well under large actuation voltages. The proposed framework can also be applied to the analysis of large deformations in some other electroactive polymers.

30 citations


Cites background from "Nonlinear and time-dependent electr..."

  • ...Secondly, the strain–stress relationship of PVDF and PPy films becomes nonlinear as the strain increases [22, 23, 29, 30]....

    [...]

  • ...To capture the nonlinear strain–stress relationship of the PVDF and PPy as the strain increases [22, 23, 29, 30], the energy functions for PVDF and PPy layers are assumed to be of neoHookean type [35], which means that they take the general form Ŵ = μ 2 (I1 − 3ν), (52)...

    [...]

Journal ArticleDOI
TL;DR: In this article, a PVDF/Metglas/PZT magnetoelectric composite was designed and characterized by modulating the DC electric fields applied on PZT, and the maximum ME coefficient (α ME ) larger than 2.0 was realized in a wide range of bias DC magnetic fields from 2 Oe to 33 Oe.

12 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the authors derived the nonlinear differential equations and boundary conditions in small-field variables, for small fields superposed on large static biasing states, from general rotationally invariant nonlinear electroelastic equations derived previously.
Abstract: The nonlinear differential equations and boundary conditions in small‐field variables, for small fields superposed on large static biasing states, are obtained from general rotationally invariant nonlinear electroelastic equations derived previously. The small‐field equations are directly applicable in the consistent description of parametric effects in high‐coupling piezoelectric materials in terms of the fundamental material parameters. The application of the equations to homogeneously polarized ferroelectrics reveals that in the linear limit the electroelastic equations are identical with the equations of linear piezoelectricity for the symmetry of the polarized state. The influence of a thickness directed homogeneous biasing electric field on the thickness vibrations of a piezoelectric plate, to second order in the biasing field, has been determined. To first order in the biasing field the results indicate that the effective fifth‐rank tensor assumed in earlier quasilinear work on the subject did not have correct symmetry properties because the influence of the homogeneous static deformation under the biasing field was ignored.

274 citations

Journal ArticleDOI
TL;DR: In this article, a consistent experimental program has been developed to investigate the mechanical and electrical properties of polyvinylidene fluoride (PVDF), and the results of the study indicate that this piezoelectric polymer can be characterized as an orthotropic, thermorheologically simple material with constant PDE strain coefficients over the experimental range of stresses, frequencies and temperatures.
Abstract: A consistent experimental program has been developed to investigate the mechanical and electrical properties of polyvinylidene fluoride (PVDF). The results of the study indicate that this piezoelectric polymer can be characterized as an orthotropic, thermorheologically simple material with constant piezoelectric strain coefficients over the experimental range of stresses, frequencies and temperatures. The mechanical properties of PVDF are time-dependent and, under certain loading and temperature conditions, can be treated using the principles of linear hereditary viscoelasticity.

176 citations

Journal ArticleDOI
TL;DR: The purpose of this investigation is to measure the elastic, dielectric and piezoelectric properties over a frequency range, including the imaginary part (loss) of these properties, by ultrasonic measurements using an impedance analyzer and a least square data-fitting technique.
Abstract: Polyvinylidene fluoride (PVDF), a piezoelectric material, has many useful applications, for example, as sensors, transducers, and surface acoustic wave (SAW) devices. Models of performance of these devices would be useful engineering tools. However, the benefit of the model is only as accurate as the material properties used in the model. The purpose of this investigation is to measure the elastic, dielectric and piezoelectric properties over a frequency range, including the imaginary part (loss) of these properties. Measurements are difficult because poled material is available as thin films, and not all quantities can be measured in that form. All components of the elastic stiffness, dielectric tensor, and electromechanical coupling tensor are needed in the models. The material studied here is uniaxially oriented poled PVDF that has orthorhombic mm2 symmetry. Presented are the frequency dependence of all nine complex elastic constants, three complex dielectric constants, and five complex piezoelectric constants. The PVDF was produced at Raytheon Research Division, Lexington, MA. Measurements were made on thin films and on stacked, cubical samples. The elastic constants c/sub 44//sup D/ and c/sub 55//sup D/, the dielectric constants e/sub 11//sup T/ and e/sub 22//sup T/, as well as the piezoelectric constants g/sub 15/ and g/sub 24/ reported here have not been published before. The values were determined by ultrasonic measurements using an impedance analyzer and a least square data-fitting technique.

80 citations

Journal Article
TL;DR: In this paper, the properties of the thin-film piezoelectric polymer PVDF were examined experimentally and the results indicated that PVDF thin films are orthotropic materials and the constitutive equations of linear hereditary viscoelasticity accurately represent the time-dependent response of PVDF over a wide range of stresses, temperatures and frequencies.
Abstract: Mechanical properties of the thin film piezoelectric polymer PVDF are examined experimentally. The developed program comprising static, creep and dynamic (oscillatory) tests provides a consistent empirical data base for material characterization of the polymer: The results of the study indicate that PVDF thin films are orthotropic materials. The constitutive equations of linear hereditary viscoelasticity are shown to accurately represent the time-dependent response of PVDF over a wide range of stresses, temperatures and frequencies. The experiments indicate that the polymer exhibits thermorheologically simple behavior governed by the temperature-frequency correspondence principle.

17 citations