Effective Piezoelectric Properties Research Articles

Characterization of 0–3 piezoelectric polymer composites using FEA for biomedical transducers applications

The performance of the 0–3 piezoelectric composite consisting of two piezoelectric materials (PZT5H and PVDF) is analyzed to improve the piezoelectric properties for sensing applications using FEA and validated with the experimental and analytical results. The experimental and predicted results are showing good matches. The average piezoelectric coefficient d33 of the piezoelectric composite and the effective elastic, dielectric and piezoelectric properties of the 0–3 passive matrix piezoelectric composite were determined from the unit cell model. It is observed from the analysis that the performance of 0–3 piezo-composite has excellent piezoelectric properties and also optimized unit cell size and polymer matrix.

Numerical study to compare effective elastic, piezoelectric, and thermal properties of a gyroid triply periodic minimal surface and 0–3 piezoelectric composites with lead-free Ba(Ti 0.8 Zr 0.2)O 3 - x(Ba 0.7 Ca 0.3)Ti O 3 reinforcement

ABSTRACT The present numerical work presents a comparative study of the effective elastic, piezoelectric, and thermal properties of polyvinylidene fluoride (PVDF) matrix and Ba ( T i 0.8 Z r 0.2 ) O 3 − x ( B a 0.7 C a 0.3 ) Ti O 3 (BZT-BCT) reinforcement-based piezo-composite at different volume fractions. The effective properties are significantly influenced by the connectivity of the reinforcement phase within the matrix. In the present work, two types of connectivity have been considered, viz. triply periodic minimal surface (TPMS) interpenetrating phase composite and 0–3 connectivity. Five different volume fractions viz. 10%, 15%, 20%, 25% and 30% were considered. Effective properties were calculated at different volume fractions and for TPMS and 0–3 composite. Significant enhancement in effective properties was observed in TPMS piezo-composites compared to 0–3 piezo-composites. The present work attempts to highlight the importance of connectivity type and the combination of lead-free piezoelectric material BZT-BCT and TPMS reinforcement to achieve better piezoelectric performance.

Piezoelectric polarization induced by dual piezoelectric materials ZnO nanosheets/MoS2 heterostructure for enhancing photoelectrochemical water splitting

Zinc oxide (ZnO) has a broad range of applications in piezo-photoelectrochemical water splitting. However, the narrow light absorption range and high photogenerated carrier recombination efficiency make ZnO somewhat limited in applying piezo-photoelectrochemical water splitting. Heterogeneous structure construction is a superior handle to these two drawbacks. Herein, few-layer molybdenum disulfide (MoS2) nanospheres are compounded on ZnO nanosheets (NSs) to form a dual-piezoelectric-material heterojunction of ZnO NSs/MoS2. The photocurrent density of ZnO NSs/MoS2 reaches 0.68 mA/cm2 at 1.23 V vs. RHE under ultrasonic vibrations. It is 2.4 times higher than that of ZnO NSs under ultrasonic vibrations. The efficient piezo-photoelectrochemical performance is attributed to increased absorption range and polarization field. On the one hand, the narrow band gap of the few-layer MoS2 widens the light absorption range of ZnO. On the other hand, compared to pure ZnO NSs, ZnO NSs/MoS2 has an enhanced polarization field under ultrasonic vibrations due to the piezoelectric properties of dual piezoelectric materials, which dramatically accelerates the electron transfer and suppresses the recombination of between electrons and holes. This work provides a new approach to constructing photoelectrodes with effective piezoelectric photocatalytic properties.

Influence of fibre cross-section profile on the multi-physical properties of uni-directional composites

The present work comprehensively examines the influence of fibre-matrix interface perimeter on the multi-physical properties of uni-directional composite materials. Three-dimensional microstructures (containing fibres of triangular, elliptical, rectangular, C-shape and two-lobe cross-section shape) are analysed to evaluate effective thermal conduction, thermo-elastic and piezo-electric properties. Each of these properties is normalised with the respective property of RVE with circular fibre cross-section; These normalised properties are, objectively, compared with the normalised fibre cross-section perimeter (shape factor). For all the considered properties and fibre cross-sectional shapes, a novel observation is that the property experiences a drop (or rise) in the initial range of the shape factor but rises (or drops) monotonically afterwards. This is in contrast with the existing literature observations, where properties are understood to have only a monotonic increase/decrease with the shape factor. Further, it is observed that the magnitude of the initial drop (or rise) is sensitive to the fibre volume fraction and the fibre-matrix property contrast. In accordance with the literature, a strong correlation is observed among the variation of in-plane shear moduli, transverse thermal conduction and transverse dielectric constants.

Effect of bicontinuous minimal surface meso-scale geometry on piezoelectric performances of piezoelectric composites

This paper examines the effective piezoelectric properties of ceramic-based composite materials that contain bicontinuous minimal surface structures. Three structures are introduced bicontinuous Schwarz P, bicontinuous Gyroid, and bicontinuous I-WP and the material model is subjected to both compressive and tensile stresses. Using the finite element method, the relationship between the average piezoelectric coefficient and the volume fraction of piezoelectric ceramics is analyzed for different structures. The study reveals that the bicontinuous Gyroid structure exhibits the highest average piezoelectric coefficient of 501 pc/N under a compressive stress of 0.5 Gpa and a piezoelectric ceramic volume fraction of 50%. Additionally, the study compares the three bicontinuous minimal surface structures with 3–3 model piezoelectric composite materials (interconnected random distribution) to explore the piezoelectric ceramic transfer path and the impact of arrangement and combination on piezoelectric properties. The results show that bicontinuous minimal surface piezoelectric composite materials display superior piezoelectric properties, as demonstrated by their high piezoelectric charge coefficient, piezoelectric voltage coefficient, and energy harvesting figure of merit. Overall, this paper provides valuable insights into how the structure of piezoelectric ceramics can be altered to enhance the performance of piezoelectric composite materials.

Effective properties of graded radially polarized piezoelectric cylindrical composites

This paper presents a theoretical study of a graded piezoelectric composite consisting of an infinitely long graded radially polarized piezoelectric cylinder embedded in an isotropic elastic non-piezoelectric matrix, under an external strain field. The physical properties of the graded cylindrical inclusion have a power-law profile with respect to the cylindrical radial variable. Using the variable separation method, closed-form solutions for the elastic displacement and electrical field in the entire composite regions are derived from the governing equation. The effective elastic and piezoelectric properties of the graded piezoelectric composite are formulated and discussed. The study reveals a vanishing mechanism of effective piezoelectric response in the graded radially polarized cylindrical piezoelectric composite. In addition, the paper derives the effective elastic formulas of the graded cylindrical elastic composites for the purely elastic problem and discusses the effects of graded property parameters on the effective elastic properties.

A novel homogenization method for periodic piezoelectric composites via diffused material interface

In this article, we propose a novel homogenization method for piezoelectric composites with periodic microstructures. In the proposed homogenization method, one can find the analytical expressions for the material properties of the composites in the representative volume element (RVE) via diffused material interface method. The availability of analytical expressions for the material properties in the entire domain of the RVE enables one to determine the effective homogenized material properties with the standard finite element method. As the proposed homogenization method regularizes the discontinuity in material properties across the interfaces, there is no need to explicitly track the material interfaces while implementing the finite element method for determining the effective material properties. Hence, one can implement the proposed homogenized method for any piezoelectric composites with complicated material interfaces and determine the effective material properties. In this study, we have considered the piezoelectric composites to be comprised of periodic microstructures where the RVE constitutes a matrix with an inclusion of a specific shape. We have carried out a study on the effect of the shape of inclusion viz. square-shaped, I-shaped, T-shaped, and plus-shaped, and the size of inclusion on the effective piezoelectric material properties. We have also studied the influence of shape and size of inclusion on the electro-mechanical response of a homogenized piezoelectric continuum. To implement the proposed homogenization method, we have used Gridap, an open-source finite element toolbox in Julia that provides very compact codes freely available to all the researchers and makes a third-party verification of the proposed method straightforward.

Negative Poisson’s ratio polyethylene matrix and 0.5Ba(Zr0.2 Ti0.8) O3–0.5(Ba0.7 Ca0.3)TiO3 based piezocomposite for sensing and energy harvesting applications

Finite element studies were conducted on 0.5Ba(Zr0.2 Ti0.8) O3–0.5(Ba0.7 Ca0.3)TiO3 (BCZT) piezoelectric particles embedded in polyethylene matrix to create a piezocomposite having a positive and negative Poisson's ratio of −0.32 and 0.2. Polyethylene with a positive Poisson's ratio is referred to as non-auxetic while those with negative Poisson's ratio are referred to as auxetic or inherently auxetic. The effective elastic and piezoelectric properties were calculated at volume fractions of (4%, 8% to 24%) to study their sensing and harvesting performance. This study compared lead-free auxetic 0–3 piezocomposite for sensing and energy harvesting with non-auxetic one. Inherently auxetic piezocomposites have been studied for their elastic and piezoelectric properties and improved mechanical coupling, but their sensing and energy harvesting capabilities and behavior patterns have not been explored in previous literatures. The effect of Poisson's ratio ranging between −0.9 to 0.4 on the sensing and energy harvesting performance of an inherently auxetic lead free piezocomposite composite with BCZT inclusions has also not been studied before, motivating the author to conduct the present study. Auxetic piezocomposite demonstrated an overall improvement in performance in terms of higher sensing voltage and harvested power. The study was repeated at a constant volume fraction of 24% for a range of Poisson's ratio varied between −0.9 to 0.4. Enhanced performance was observed at the extreme negative end of the Poisson's ratio spectrum. This paper demonstrates the potential improvements by exploiting auxetic matrices in future piezocomposite sensors and energy harvesters.

Control of the piezoelectric and flexoelectric homogenized properties of architected materials by tuning their inner topology

The present contribution aims to study the effect the inner topology of periodic architected materials on their effective piezoelectric and flexoelectric properties. An analysis is performed to study the sensitivity of the effective flexoelectric moduli to the geometrical variables of the considered unit cells of periodic lattice materials. More specifically, hexagonal, re-entrant auxetic, and rectangular unit cells are investigated in terms of their relative piezoelectric and flexoelectric response. The base material obeys a piezoelectric behavior, and the homogenized electromechanical properties are evaluated using the extended Hill–Mandel macrohomogeneity condition articulated with variational principles in the context of periodic multiphysical homogenization. The developed modeling framework of coupled electromechanical phenomena accounts for the higher gradient effects modeled by flexoelectricity that are induced by the strong gradient of properties that exist at the microlevel of the lattice unit cell. Regular hexagonal, re-entrant hexagonal and rectangular lattice unit cells are mutually compared in terms of their flexoelectric properties. The regular hexagonal UC shows the highest piezoelectric moduli, whereas the flexoelectric moduli are found to be maximum for the re-entrant UC. The coupling between mechanical and electrical fields is attested by the non-uniform distribution of the electric potential within the three studied architected materials subjected to a uniform strain.

Sound Absorption Improvement in Porous Ferroelectret Polyethylene with Effective Piezoelectric Mechanism.

Airborne sound absorption in porous materials involves complex mechanisms of converting mechanical acoustic energy into heat. In this work, the effective piezoelectric properties of polyethylene ferroelectret foams on sound absorption were investigated by comparable samples with and without the piezoelectric response. Corona poling and thermal annealing treatments were applied to the samples in order to enable and remove the piezoelectric property, respectively, while the microstructure and the mechanical properties remained substantially unchanged. The effective piezoelectric properties and airborne sound absorption coefficients of the polyethylene foam samples before and after material treatments were measured and analyzed. Our experimental results and theoretical analysis showed that the open-cell ferroelectret polymer foam with an effective piezoelectric property provides an additional electromechanical energy conversion mechanism to enhance the airborne acoustic absorption performance.

Interdependent effects of surface and flexoelectricity on the electromechanical behavior of BNRC nanoplate

The present work deals with the static and dynamic behavior of boron-nitride (BN) reinforced piezoelectric nanocomposite subjected to mechanical load while considering flexoelectric and surface effects. Based on the modified Kirchhoff plate theory and Navier's solution, an analytical model is derived to investigate the electromechanical response of simply supported (SS) boron-nitride reinforced nanocomposite (BNRC) plates. In addition, a micromechanical model by employing the Mori-Tanaka (MT) approach is derived to investigate the effective elastic and piezoelectric properties of the BNRC lamina. The BNRC lamina is composed of BN nanofiber and polyimide matrix, such that the BN nanofibers are oriented along the 3-direction. Our outcomes reveal that the incorporation of the BN nanofiber shows a substantial enhancement in the effective longitudinal and transverse piezo-elastic coefficients of the BNRC lamina. Further, the outcomes of the analytical model by adopting the Kirchhoff plate theory illustrate that the effects of flexoelectricity and surface show significant enhancement in the stiffness of the composite at the nanoscale, although the surface effect is more pronounced when compared with the flexoelectric effect. Based on the present analysis, we observed that the effects of flexoelectricity and surface influence the static and vibrational properties of BNRC. Thus, at the nanoscale, these size-dependent properties cannot be neglected. This work presents an opportunity for the development of high-performance and efficient BNRC nanoplates.

Micromechanics predictions of effective elastic, piezoelectric and dielectric properties of composite piezoelectric films

Knowledge of the effective elastic, piezoelectric and dielectric properties facilitates the design of radio frequency devices, for example film bulk acoustic resonators (FBARs). Based on the Reuss model and Eshelby–Mori–Tanaka micromechanics theory, this paper predicts the effective properties of bilayer composite piezoelectric film consisting of AlN film and vertical compound ScAlN film. The evaluated material coefficients and original material parameters are substituted into the FEM simulation to investigate the performance of FBARs, respectively. The consistent resonant frequencies of FBARs demonstrate the accuracy of Reuss model in calculating the effective parameters of bilayer composite piezoelectric film.

Determination of multi-physics effective properties, and actuation response of triply periodic minimal surface based novel photostrictive composites: A finite element analysis

This paper presents the novel triply periodic minimal surface (TPMS) based photostrictive composite as an alternative to naturally occurring photostrictive materials. The non-thermal, light-induced mechanical strain i.e., photostriction involves the simultaneous action of photovoltaic effect and converse piezoelectric effect. All the effective elastic, dielectric, piezoelectric, and pyroelectric properties are evaluated using the finite element analysis and compared with traditional micromechanical models for fibrous composites. Degenerated shell element is used to simulate the actuation response of unimorph cantilever and simply supported beams bonded with TPMS based photostrictive composite. The proposed photostrictive composite consists of poly{4,8-bis[5-(2-ethyl-hexyl) thiophen-2-yl] benzo[1,2-b:4,5-b’] dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethyl-hexyl) carbonyl] thieno[3,4-b] thiophene-4,6-diyl} (PTB7-Th) as photovoltaic polymer matrix and Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 (PMN-35PT) as TPMS—based filler material. The proposed TPMS based photostrictive composite induces 10 times larger actuation than 0–3 photostrictive composite. Also, the maximum deflection (3.22×10−5 m) of cantilever smart beam, achieved with Schoen-I-WP based photostrictive composite, is more than that achieved with Schoen-gyroid based photostrictive composite i.e., 2.78×10−5 m. Similar trends are obtained for simply supported smart beam where the center deflection for Schoen-I-WP based photostrictive composite and Schoen-gyroid based photostrictive composite are found to be 4.04×10−6 m and 3.49×10−6 m, respectively. The proposed novel photostrictive composite has potential for future wireless actuation applications.

Optimizing Piezoelectric Nanocomposites by High‐Throughput Phase‐Field Simulation and Machine Learning (Adv. Sci. 13/2022)

Optimizing Piezoelectric Nanocomposites In article number 2105550, Tiannan Yang, Zhao Kang, Long-Qing Chen, Yuanjie Su, Zijian Hong, and co-workers conduct an integrated study with high-throughput phase-field simulations and machine learning to systematically reveal the influence of morphology and spatial orientation of an oxide filler on the effective piezoelectric properties of the polymer/ferroelectric oxide nanocomposites.

Numerical investigation of sensing and energy harvesting performance of 0-3 and triply periodic minimal surface-based K0.475Na0.475Li0.05(Nb0.92Ta0.05Sb0.03)O3 and polyethylene piezocomposite: A comparative study

The present paper is devoted to conducting a comparative study on the sensing and energy harvesting performance of a 0-3 and triply periodic minimal surface (TPMS)-based piezocomposite with [Formula: see text] ( KNLNTS) material as piezoelectric inclusions and polyethylene as the matrix material. Different types of TPMS are reported in literature like Neovius, Fischer-Koch S, Schwarz CLP, Schoen Gyroid, Schoen IWP, Schwarz Primitive, etc. In the present study, Schwarz primitive TPMS is considered. Representative volume elements (RVEs) with four different volume fractions are generated and the finite element simulations are performed to compute the effective elastic and piezoelectric properties. The homogenization technique is used to calculate the effective properties. The calculated values of the effective properties are further used to calculate the sensing voltage between the electrodes and harvested power across the resistance. The effective elastic and piezoelectric properties increase with an increase in volume fraction of the piezoelectric inclusions resulting in a higher sensing voltage and power. Significant improvement in the effective elastic and piezoelectric properties of TPMS-based piezocomposite was observed. TPMS-based piezocomposite exhibited superior performance as compared to their 0-3 counterparts.

Construction of piezoelectric and flexoelectric models of composites by asymptotic homogenization and application to laminates

The effective piezoelectric and flexoelectric properties of heterogeneous solid bodies with constituents obeying a piezoelectric behavior are evaluated in full generality, based on the asymptotic expansion method. The successive situations of materials obeying a piezoelectric and flexoelectric behavior at the macroscale is envisaged in the present work. Closed-form expressions for the effective flexoelectric properties are obtained for stratified materials. A general theory for laminated piezoelectric plates is formulated on the basis of the formulated asymptotic models, and the response of the homogeneous substitution plate is evaluated for a loading consisting of a pure bending moment, triggering electric fields and strain and electric fields gradients within the plate thickness. The local mechanical and electric fields at the microscopic level within the initial heterogeneous stratified domain are evaluated by solving unit cell boundary value problems for the localization operators. An effective flexoelectric plate model for a stratified composite is constructed, showing the generation of the gradient of an electric field under application of a pure bending moment.

Novel photostrictive 0-3 composites: A finite element analysis

Simultaneous action of photovoltaic effect and converse piezoelectric effect will induce the photostrictive effect. In contrast to the naturally occurring photostrictive material, the present study proposes a 0-3 photostrictive composite. The current photostrictive composite comprises of poly{4,8-bis[5-(2-ethyl-hexyl) thiophen-2-yl] benzo[1,2-b:4,5-b′] dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethyl-hexyl) carbonyl] thieno[3,4-b] thiophene-4,6-diyl} (PTB7-Th) as organic photovoltaic polymer matrix and Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-35PT) as the particulates. The current study shows that the present 0-3 photostrictive composite is a suitable alternative for the most popular lead-based photostrictive material. While evaluating all the effective elastic, dielectric, piezoelectric, and pyroelectric properties of 0-3 photostrictive composite, the effect of local fluctuations was incorporated in representative volume element (RVE) using the finite element method. A finite element formulation using a degenerated shell element is derived to simulate the actuation response of the proposed 0-3 photostrictive composite. Numerical studies have been performed on cantilever and simply supported beams. The maximum tip and center deflection of cantilever beam and simply supported beam bonded with 0-3 photostrictive patch is mm and mm, respectively. The maximum value of the effective piezoelectric coefficient effective thermal expansion coefficient effective Young’s modulus and effective pyroelectric coefficient of proposed 0-3 photostrictive composite are m/V, 4.59 1.63 N/m2, and 7.57 C/m2 K, respectively, obtained at 25% volume fraction of particulates. This study opens possibilities of photostrictive coupling in composites.

Topology optimization of flexoelectric composites using computational homogenization

We present a topology optimization framework to design periodic composites comprised of piezoelectric constituents that exhibit large flexoelectric constants. The novelty of the approach is that it leverages a representative volume element (RVE)-based computational homogenization approach that enables the analysis of periodic composites where the characteristic dimensions of the microstructure are significantly smaller than those of the structure, and as such requires only the optimization of a single RVE rather than that of the entire structure. We utilize this approach to analyze the enhancement in flexoelectric constants that can be achieved in different types of PZT-based composites, including hard–hard (PZT–PZT), and hard–soft (PZT–polymer composite, and porous PZT) structures. In all cases, significant enhancements are observed, with improvements between 2 and 15 times those of a naive guess, with some designs reaching a factor of one order of magnitude larger than BTO. We identify different mechanisms governing the enhanced electromechanical couplings, which can arise either from an enhancement of effective piezoelectricity in the RVE for PZT–PZT composites, or from a more subtle interplay involving the enhancement of effective piezoelectric and dielectric properties coupled with a reduction in mechanical compliance for PZT–polymer and porous PZT RVEs.

Lead-free 0–3-type composites: From piezoelectric sensitivity to modified figures of merit

Effective piezoelectric properties, electromechanical coupling factors (ECF) and figures of merit (FOM) are studied in lead-free 0–3-type composites based on novel ferroelectric 0.965([Formula: see text][Formula: see text]([Formula: see text][Formula: see text]O3–0.035[Formula: see text][Formula: see text][Formula: see text][Formula: see text]O3 ceramic. Systems of prolate ceramic inclusions are surrounded by a large polymer matrix that can be either monolithic (in the 0–3 composite) or porous (in the 0–3–0 composite). Non-monotonic volume-fraction dependences of the effective piezoelectric coefficients [Formula: see text], ECF [Formula: see text], squared FOM [Formula: see text] and their modified analogs for stress-driven systems are analysed, and examples of the high longitudinal piezoelectric sensitivity ([Formula: see text][Formula: see text] 100 mV ⋅m/N) are considered. A role of microgeometrical factors, that promote the large effective parameters and anisotropy of properties in the 0–3-type composites, is highlighted. New “aspect ratio — volume fraction” diagrams are first built to describe conditions for high piezoelectric sensitivity, large modified FOM and their anisotropy in the studied composites. These advanced materials can be of value for piezoelectric sensor, energy-harvesting and related applications.

Micromechanical modeling approach with simplified boundary conditions to compute electromechanical properties of architected piezoelectric composites

Architected piezoelectric composites (PCs) have recently gained interest in designing transducers and nondestructive testing devices. The current analytical modeling approach cannot be readily applied to design architected periodic PCs exhibiting elastic anisotropy and piezoelectric activity. This study presents a micromechanical (MM)-model based finite element (FE) modeling framework to predict the electromechanical properties (EMPs) of the architected PCs. As an example, the microstructure with one-dimensional (1–3 PCs) connectivity is considered with different cross-sections of fibers. 3D FE models are developed. The intrinsic symmetry of architected composite is used to derive boundary conditions (BCs) equivalent to periodic BCs (PBCs). The proposed approach is simple and eliminates the need for a tedious mesh generation process on opposite boundary faces on the MM model of architected PCs. The EMPs of 1–3 PCs calculated from the proposed micromechanics-FE models were compared with those obtained from analytical solutions (i.e. based on micromechanics theories), and FE homogenization (i.e. obtained by employing the PBCs available in the literature). A quite good agreement between the proposed modeling approach and the ones obtained using the analytical model was observed. However, an excellent agreement is observed with the MM results that employed PBCs. Hence, we have concluded that the proposed MM modeling approach is equivalent to MM models that employed PBCs. The computed enhanced effective elastic, piezoelectric, and dielectric properties and corresponding figure of merit revealed that 1–3 PCs are suitable in transducer applications.