Overall electroelastic moduli of particulate piezocomposites with non-dilute BCC microstructure (original) (raw)
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Numerical representative volume element (RVE) models using ANSYS® finite element package are developed for 1–3 periodic composites made of piezoelectric (PZT) fibers embedded in a soft non-piezoelectric matrix (polymer matrix). The RVE method is used to predict the effective electromechanical coefficients of the periodic transversely isotropic piezoelectric cylindrical fiber composite. Special emphasis is placed on the formulation of the boundary conditions that allows the simulation of all modes of overall deformation arising from any arbitrary combination of mechanical and electrical loading. This numerical approach allows the extension to composites with arbitrary geometrical inclusion configurations, providing a powerful tool for fast calculation of their effective coefficients. The effective coefficients for hexagonal arrangements of unidirectional piezoelectric cylindrical fiber composites are evaluated for different fiber volume fractions. Then, for verification the homogeniz...
Journal of Applied Physics, 2013
In this work, the piezoelectric properties at high electric fields of dielectrophoretically aligned PZT-polymer composites containing high aspect ratio particles (such as short fibers) are presented. Polarization and strain as a function of electric field are evaluated. The properties of the composites are compared to those of PZT-polymer composites with equiaxed particles, continuous PZT fiber-polymer composites, and bulk PZT ceramics. From high-field polarization and strain measurements, the effective field dependent permittivity and piezoelectric charge constant in the poling direction are determined for dielectrophoresis structured PZT-polymer composites, continuous PZT fiber-polymer composites, and bulk PZT ceramics. The changes in dielectric properties of the inclusions and the matrix at high fields influence the dielectric and piezoelectric properties of the composites. It is found that the permittivity and piezoelectric charge constants increase towards a maximum at an applied field of around 2.5-5 kV/mm. The electric field at which the maximum occurs depends on the aspect ratio and degree of alignment of the inclusions. Experimental values of d 33 at low and high applied fields are compared to a model describing the composites as a continuous polymer matrix containing PZT particles of various aspect ratios arranged into chains. Thickness mode coupling factors were determined from measured impedance data using fitted equivalent circuit model simulations. The relatively high piezoelectric strain constants, voltage constants, and thickness coupling factors indicate that such aligned short fiber composites could be useful as flexible large area transducers. V
On the modeling and design of piezocomposites with prescribed properties
Archive of Applied Mechanics (Ingenieur Archiv), 2001
Piezoelectric transversely isotropic matrix containing spheroidal piezoelectric inclusions with different properties and of, generally, diverse aspect ratios is considered. A full set of ten effective electrostatic constants is derived, using the method of effective ®eld. The case, when the inclusions are circular cylinders (®bers) is analyzed in detail. The results are compared with those of several earlier works. They constitute the theoretical framework for the design of piezocomposites with prescribed overall properties.
Electric field structuring of piezoelectric composite materials
Journal- Korean Physical Society
Piezoelectric composite materials, consisting of a ferroelectric ceramic in an electrically-inactive polymer matrix, have been shown to greatly outperform single phase materials for certain applications. A new assembly technique, which electrically controls the spatial distribution of the ceramic within the polymer, promises to enhance the sensitivity of 0-3 type piezoelectric composites. The materials so-produced have a quasi 1-3 structure and it is intended that they will exhibit some of the advantages of 1-3 piezoelectric composites, whilst retaining the simplicity of 0-3 manufacturing. My heartfelt thanks to all of those people who have helped me to complete this study. To Roger Whatmore, for giving me the opportunity to study at Cranfield and for his support, his advice, his patient supervision and many words of encouragement. To George Maistros for his lasting support and his technical expertise in dielectrics. To Harry Block for his inspiration and his enthusiasm. To the technical staff in the School of Industrial and Manufacturing Science and most especially to Andrew Stallard, who have contributed to this research in so many ways. To the academic and research staff in the Advanced Materials Group for their help and advice and to my colleagues in the Nanotechnology Group. The work detailed in this thesis was undertaken on an EPSRC Case Studentship and supported financially by DERA. Particular thanks must go to my industrial supervisor at the Structural Materials Centre, Steve Mahon for his support, for his experience and guidance, for providing materials and test facilities. I am grateful for his faith in my ability. Special thanks to Dan Campbell of the Open University who got me started in materials and to my friend Hil, who has been there throughout my academic career. Finally I must also thank my family for the love and support that they have given me over the years. E ferro ferrum temperatum After the fire, the fire still burns. Contents 1. 2.7.1 Ceramic Phase 11 2.7.2 Polymer Phase 12 2.7.3 Ceramic-polymer Interface 12 2.7.4 Composite Preparation 12 2.7.5 Poling of Composites 3. Assembly of Composite Materials using the Dielectrophoretic Effect-A Review 14 4. Modus Operandi 17 4.1 Critique of Published Work 17 4.2 Overview of the Current Project 18 4.3 Notes on Practical Aspects of the Project 19 4.3.1 Filler Materials 19 4.
Finescaled piezoelectric 1–3 composites: properties and modeling
Journal of the European Ceramic Society, 1999
Composites consisting of ®ne, unidirectional ordered piezoelectric ®bers in a polymer matrix oer a series of commercially relevant applications. Making use of PZT ®bers with diameters in the range of 10± 50 mm improved functional properties of such 1±3 composites are expected, stimulating the development of advanced ultrasonic transducers. The present paper reports on the preparation of 1±3 composites with dierent volume fractions of PZT(53/47) ®bers and the characterization of their dielectric and piezoelectric properties. The experimental data were compared with results of ®nite element method modeling and parallel circuit modeling.
Composite Structures, 2014
In this paper, the time and frequency dependent effective behaviors of multi-phase and multicoated viscoelectroelastic composites are investigated. The correspondence principle, extended to linear viscoelectroelasticity, and the Mori-Tanaka micromechanical mean field approach are used. Based on integral equations and on the obtained viscoelectroelastic interfacial operators closed form expressions of the concentration tensors for viscoelectroelastic composites are derived. The effective properties are obtained in the Carson domain and then inverted numerically to the time domain. They are presented in frequency and time domains for various types, shapes and volume fractions of inclusions as well as for various thicknesses of the coating and showed relaxation effects on all resultant electroelastic coefficients. The frequency dependent storage and loss factors of the obtained effective electroelastic coefficients as well as their cycle limits are elucidated. By this methodological approach, new hybrid composite materials can be obtained and their active-passive properties can be optimized with respect to phase, coating layer and inclusion characteristics.
Novel poling method for piezoelectric 0–3 composites and transfer to series production
Sensors and Actuators A: Physical, 2018
Integration of piezoceramic particles into polymers is considered to meet current and future challenges of function integration in lightweight engineering. Especially composites with integrated piezoceramic transducers for sensory tasks such as condition or structural health monitoring are gaining importance. A possible, mass production compatible manufacturing approach is the direct formation of a piezoceramic particle-electrode-assembly during the processing by integrating the ceramic and its electrodes into the polymer matrix. The piezoelectric particles are then fully surrounded by the polymer matrix, forming a socalled 0-3 composite (Newnham et al., 1978). However, it is unpoled and inactive and thus requires poling to activate the piezoelectric properties. It is known that poling of piezoelectric particles in a polymer matrix is difficult due to the misfit in dielectric constants of polymer and ceramic. To overcome this obstacle, a poling process that is conducted during the uncured stage of the polymer matrix is introduced in the present paper, making use of the relatively low electrical resistance of the selected polymer in the uncured state. In a first step, the method is modelled and experimentally verified using specimen made of PZT pearls embedded in epoxy resin. In these preliminary experiments, effective piezoelectric charge coefficients up to 28.6 pC/N were achieved. The method is transferred and integrated into the production of fibre-reinforced polyurethane composites. Effective piezoelectric charge coefficients of 5.5 pC/N are obtained for the polyurethane based composites.
On the possibility of piezoelectric nanocomposites without using piezoelectric materials
Journal of The Mechanics and Physics of Solids, 2007
In this work, predicated on nanoscale size-effects, we explore the tantalizing possibility of creating apparently piezoelectric composites without using piezoelectric constituent materials. In a piezoelectric material an applied uniform strain can induce an electric polarization (or vice-versa). Crystallographic considerations restrict this technologically important property to non-centrosymmetric systems. Non-uniform strain can break the inversion symmetry and induce polarization even in non-piezoelectric dielectrics. The key concept is that all dielectrics (including non-piezoelectric ones) exhibit the aforementioned coupling between strain gradient and polarization-an experimentally verified phenomenon known in some circles as the flexoelectric effect. This flexoelectric coupling, however, is generally very small and evades experimental detection unless very large strain gradients (or conversely polarization gradients) are present. Based on a field theoretic framework and the associated Greens function solutions developed in prior work, we quantitatively demonstrate the possibility of ''designing piezoelectricity,'' i.e. we exploit the large strain gradients present in the interior of composites containing nanoscale inhomogeneities to achieve an overall non-zero polarization even under an uniformly applied stress. We prove that the aforementioned effect may be realized only if both the shapes and distributions of the inhomogeneities are non-centrosymmetric. Our un-optimized quantitative results, based on limited material data and restrictive assumptions on inhomogeneity shape and distribution, indicate that apparent piezoelectric behavior close to 10% of Quartz may be achievable for inhomogeneity sizes in the 4 nm range. In future works, it is not ARTICLE IN PRESS www.elsevier.com/locate/jmps 0022-5096/$ -see front matter r unreasonable to expect enhanced performance based on optimization of shape, topology and appropriate material selection.
Composites Part A: Applied Science and Manufacturing, 2012
Three phase epoxy/piezoelectric/conductive filler composites were fabricated. The volume fraction of the conductive filler, aluminum, was held constant at 20%, while the volume fraction of the piezoelectric material, PZT was varied from 0.10 to 0.70. Three sets of composites were examined, wherein, the size of the aluminum constituent was varied from micron in size (200 mesh) to nano -in size ($18 nm). Both sets of composites presented enhanced loss factor (tan d) and piezoelectric coefficient (d33) values for volume fractions of PZT above 0.30 volume fraction. Composites having micron size aluminum particles exhibited higher loss factor and strain coefficients than those that incorporated nano-size aluminum particles, which could be due to several factors: agglomeration, contact resistance between particles, and excess air voids in the samples.