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Piezocomposites with both flexibility and electromechanical conversion characteristics have been widely applied in various fields, including sensors, energy harvesting, catalysis, and biomedical treatment. In the composition of piezocomposites or their preparation process, a category of materials is commonly employed that do not possess piezoelectric properties themselves but play a crucial role in performance enhancement. In this review, the concept of auxiliary phase is first proposed to define these materials, aiming to provide a new perspective for designing high‐performance piezocomposites. Three different categories of modulation forms of auxiliary phase in piezocomposites are systematically summarized, including the modification of piezo‐matrix, the modification of piezo‐fillers, and the construction of special structures. Each category emphasizes the role of the auxiliary phase and systematically discusses the latest advancements and the physical mechanisms of the auxiliary phase enhanced flexible piezocomposites. Finally, a summary and future outlook of piezocomposites based on the auxiliary phase are provided. [ABSTRACT FROM AUTHOR]

Multirotor vehicles typically use either complex mechanisms to vary blade pitch angle or speed control to vary thrust and torque to attain stability and maneuverability. Alternatively, thrust and torque can be varied by morphing the blades without the use of complex mechanisms and without varying the rotor speed. This method could be faster to change thrust, more efficient, and it may require fewer mechanical components. This paper presents an experimentally validated aerodynamic model with an empirical static-aeroelastic correction to predict the thrust and torque coefficient of a mechanism-free rotor with Macro-Fiber Composite actuators. A variable-camber piezocomposite rotor prototype is experimentally tested on a static-thrust setup. The experiment is used to identify the so-called unknown coefficients of the model (e.g., related to the shape of the blade induced by the piezoelectric device) and to identify a correction to account for flow-induced deformations. Using the identified model, several parametric analyses are conducted to predict thrust and torque coefficients as a function of rotor speed and the electrical excitation of the piezocomposite actuators. In addition, the model is used for design optimization, leading to several optimal designs based on a limited parameter space. Three different objective functions are used: maximizing thrust, minimizing torque, and maximizing thrust-to-torque ratio. The operational aerodynamic characteristics of these designs are also presented. [ABSTRACT FROM AUTHOR]

This paper introduces a coupled electromechanical finite deformation phase field model for crack propagation and interfacial decohesion in multiphase piezoelectric composites with interfaces. The crack phase field model is augmented with cohesive traction-separation laws at the material interfaces, derived from a cohesive potential function. A Gibbs free energy density function is proposed, allowing for the incorporation of the anisotropic elastic stiffness of the piezoelectric material. Numerical simulations exhibiting different failure mechanisms are carried out to demonstrate the efficacy of the model. Effects of external electric field on crack evolution and the competition between penetration and deflection of a crack impinging on an interface are investigated. Limited verification tests are conducted with theoretical results. Finally, the model is used to simulate fracture in nonuniform piezocomposite microstructures. The effect of crack propagation on the evolution of the electric field with different crack face conditions are analyzed. Differences in the electromechanical responses of piezocomposites due to different fiber distributions are also observed. [ABSTRACT FROM AUTHOR]

In the present numerical simulation work, effective elastic and piezoelectric properties are calculated and a comparative study is conducted on a cement matrix‐based piezocomposite with 0–3 and gyroid triply periodic minimal surface (TPMS) inclusions. The present study compares the effective properties of different piezoelectric materials having two different types of connectivity of the inclusions namely, 0–3 inclusions where the inclusions are physically separated from each other and are embedded within the matrix and the second one is TPMS inclusions having interpenetrating phase type connectivity. Effective properties are calculated for four different materials at five different volume fractions namely, 10%, 15%, 20%, 25%, and 30% volume fractions of inclusion by volume. In terms of effective properties and direct piezoelectric effect, TPMS piezocomposite is found to perform better compared to 0–3 piezocomposite. Lead‐free piezoelectric material 0.5Ba(Ca0.8Zr0.2)O3 − 0.5(Ba0.7Ca0.3)TiO3 demonstrates better performance compared to all other material inclusions studied. The present study attempts to highlight improved piezoelectric effective properties of lead‐free material‐based piezocomposites with TPMS inclusions. [ABSTRACT FROM AUTHOR]

Lead-free piezoceramics are gaining interest in the field of bone tissue engineering due to their surface charges and improved bone cell adhesion. However, monolithic materials are less suitable for more complex medical conditions, as the properties must be tailored and locally adaptable. Therefore, we designed a modular composite of ceramic building blocks and polymer-matrix to customize the piezoelectric properties with individual polarization of each block, while maintaining the benefits of each phase. Barium titanate building blocks were prepared by injection molding and were assembled into 2-2-layered and modular structures, which were bonded with barium titanate-filled (ΦP = 35 vol %) epoxy resin. The piezoelectric response was determined using direct excitation via Berlincourt method, and the influence of the matrix thickness as well as the different polarization orientations of individual building blocks was investigated.

Abstract In the present numerical simulation work, effective elastic and piezoelectric properties are calculated and a comparative study is conducted on a cement matrix‐based piezocomposite with 0–3 and gyroid triply periodic minimal surface (TPMS) inclusions. The present study compares the effective properties of different piezoelectric materials having two different types of connectivity of the inclusions namely, 0–3 inclusions where the inclusions are physically separated from each other and are embedded within the matrix and the second one is TPMS inclusions having interpenetrating phase type connectivity. Effective properties are calculated for four different materials at five different volume fractions namely, 10%, 15%, 20%, 25%, and 30% volume fractions of inclusion by volume. In terms of effective properties and direct piezoelectric effect, TPMS piezocomposite is found to perform better compared to 0–3 piezocomposite. Lead‐free piezoelectric material 0.5Ba(Ca0.8Zr0.2)O3 − 0.5(Ba0.7Ca0.3)TiO3 demonstrates better performance compared to all other material inclusions studied. The present study attempts to highlight improved piezoelectric effective properties of lead‐free material‐based piezocomposites with TPMS inclusions.

A piezoelectric Macro fiber composite (MFC) materials developed in the last decade found widespread applications such as vibration sensing, actuation and structural health monitoring. Unlike conventional ceramic piezoelectric materials (PZT), these composites show many advantages such as flexibility, reliability and high actuation capacity. However, increasing their energy harvesting capabilities still remains a challenge. Modeling and simulation of electrical energy harvesters using MFC patches provide a mean for geometrical optimization and appropriate choice of the MFC composite. This paper proposes a linear analytical model for prediction of the electro-mechanical response of bimorph harvesters using MFC patches. Homogenization technique is used to describe the equivalent piezoelectric properties of the composite structure of the MFC patch. This paper investigates the effect of the volume fraction of the fibers and the material choice of the piezoelectric fibers and epoxy matrix on the generated electrical power. It has been found that an increased fiber volume fraction causes a decrease of the voltage, the power and the velocity amplitudes for a range of load resistance. However, an increase in the fiber volume fraction FVF is achieved by an increase of the current amplitude for a range of load resistance. Maximum amount of power is generated by the bimorph MFC harvester for an FVF of 86% which corresponds to the reference configuration. The piezoelectric fiber material has a significant influence on the output power. In fact, the SONOX-P502 generated the greatest electrical power. However, the material of the matrix has a negligible effect on the generated power. [ABSTRACT FROM AUTHOR]

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 K0.475Na0.475Li0.05(Nb0.92Ta0.05Sb0.03)O3 (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. [ABSTRACT FROM AUTHOR]

The piezoelectric d ij coefficient is often regarded in materials science as the most important figure of merit of piezoelectric performance. For many applications, the piezoelectric g ij coefficient which correlates to voltage output and sensitivity of a piezoelectric material can be considered of equal or increased importance, however is often an overlooked parameter in materials science literature. The aim of this review is to highlight the importance of this parameter and to provide insight into the mechanisms that drive a high piezoelectric voltage coefficient in single crystal, polycrystalline, and composite form. For bulk ceramics, special attention is given to tetragonal systems due to the availability of electrical and crystallographic data allowing for a clear structure-property relation. Orthorhombic and rhombohedral systems are mentioned and specific cases highlighted, however investigating structure-property relations is difficult due to the lack of crystallographic datasets. Composite materials have been the forefront of high g ij piezoelectric materials over the decades and are therefore also considered in both ceramic-matrix and polymer-matrix form. An overview of applications in medical, energy, fishing and defence industries where a high g ij is desirable are considered and the scientific and commercial considerations that must be made for the transition from laboratory to industry are discussed from the perspective of integrating new piezoelectric materials into sonar devices. [ABSTRACT FROM AUTHOR]

In field applications currently used for health monitoring and nondestructive testing, ultrasonic transducers primarily employ PZT5-H as the piezoelectric element for ultrasound transmission and detection. This material has a Curie–Weiss temperature that limits its use to about 210 °C. Some industrial applications require much higher temperatures, i.e., 1000–1200 °C and possible nuclear radiation up to 1020 n/cm2 when performance is required in a reactor environment. The goal of this paper is the survey and review of piezoelectric elements for use in harsh environments for the ultimate purpose for structural health monitoring (SHM), non-destructive evaluation (NDE) and material characterization (NDMC). The survey comprises the following categories: 1. High-temperature applications with single crystals, thick-film ceramics, and composite ceramics, 2. Radiation-tolerant materials, and 3. Spray-on transducers for harsh-environment applications. In each category the known characteristics are listed, and examples are given of performance in harsh environments. Highlighting some examples, the performance of single-crystal lithium niobate wafers is demonstrated up to 1100 °C. The wafers with the C-direction normal to the wafer plane were mounted on steel cylinders with high-temperature Sauereisen and silver paste wire mountings and tested in air. In another example, the practical use in harsh radiation environments aluminum nitride (AlN) was found to be a good candidate operating well in two different nuclear reactors. The radiation hardness of AlN was evident from the unaltered piezoelectric coefficient after a fast and thermal neutron exposure in a nuclear reactor core (thermal flux = 2.12 × 1013 ncm−2; fast flux 2 (>1.0 MeV) = 4.05 × 1013 ncm−2; gamma dose rate: 1 × 109 r/h; temperature: 400–500 °C). Additionally, some of the high-temperature transducers are shown to be capable of mounting without requiring coupling material. Pulse-echo signal amplitudes (peak-to-peak) for the first two reflections as a function of the temperature for lithium niobate thick-film, spray-on transducers were observed to temperatures of about 900 °C. Guided-wave send-and-receive operation in the 2–4 MHz range was demonstrated on 2–3 mm thick Aluminum (6061) structures for possible field deployable applications where standard ultrasonic coupling media do not survive because of the harsh environment. This approach would benefit steam generators and steam pipes where temperatures are above 210 °C. In summary, there are several promising approaches to ultrasonic transducers for harsh environments and this paper presents a survey based on literature searches and in-house laboratory observations. [ABSTRACT FROM AUTHOR]

In field applications currently used for health monitoring and nondestructive testing, ultrasonic transducers primarily employ PZT5-H as the piezoelectric element for ultrasound transmission and detection. This material has a Curie–Weiss temperature that limits its use to about 210 °C. Some industrial applications require much higher temperatures, i.e., 1000–1200 °C and possible nuclear radiation up to 1020 n/cm2 when performance is required in a reactor environment. The goal of this paper is the survey and review of piezoelectric elements for use in harsh environments for the ultimate purpose for structural health monitoring (SHM), non-destructive evaluation (NDE) and material characterization (NDMC). The survey comprises the following categories: 1. High-temperature applications with single crystals, thick-film ceramics, and composite ceramics, 2. Radiation-tolerant materials, and 3. Spray-on transducers for harsh-environment applications. In each category the known characteristics are listed, and examples are given of performance in harsh environments. Highlighting some examples, the performance of single-crystal lithium niobate wafers is demonstrated up to 1100 °C. The wafers with the C-direction normal to the wafer plane were mounted on steel cylinders with high-temperature Sauereisen and silver paste wire mountings and tested in air. In another example, the practical use in harsh radiation environments aluminum nitride (AlN) was found to be a good candidate operating well in two different nuclear reactors. The radiation hardness of AlN was evident from the unaltered piezoelectric coefficient after a fast and thermal neutron exposure in a nuclear reactor core (thermal flux = 2.12 × 1013 ncm−2; fast flux 2 (>1.0 MeV) = 4.05 × 1013 ncm−2; gamma dose rate: 1 × 109 r/h; temperature: 400–500 °C). Additionally, some of the high-temperature transducers are shown to be capable of mounting without requiring coupling material. Pulse-echo signal amplitudes (peak-to-peak) for the first two reflections as a function of the temperature for lithium niobate thick-film, spray-on transducers were observed to temperatures of about 900 °C. Guided-wave send-and-receive operation in the 2–4 MHz range was demonstrated on 2–3 mm thick Aluminum (6061) structures for possible field deployable applications where standard ultrasonic coupling media do not survive because of the harsh environment. This approach would benefit steam generators and steam pipes where temperatures are above 210 °C. In summary, there are several promising approaches to ultrasonic transducers for harsh environments and this paper presents a survey based on literature searches and in-house laboratory observations. [ABSTRACT FROM AUTHOR]

Piezocomposites composed of piezoelectric inorganic particles dispersed in a flexible polymer have emerged as promising materials for flexible energy harvesters and sensors. In this work, to overcome the inefficient stress transfer capability in flexible piezocomposites for energy harvester, KNbO3 (KN) particles prepared by conventional solid oxide process were aligned to form chain‐distributed particles in polydimethylsiloxane (PDMS) matrix by dielectrophoresis. The composite with 8 vol.‐% KN has peak open circuit voltage of 6.3 V and short‐circuit current of 0.82 µA under an applied force of 7 N, which are significantly improved in compared with the sample with piezoelectric particles randomly dispersed. Hugely enhanced stress‐transfer capability of the aligned composite plays a key role in achieving large piezoelectric response. This work provides a promising material candidate for high performance flexible energy harvester. [ABSTRACT FROM AUTHOR]

The paper describes the results of the experimental study of the properties of piezoceramics, ceramic matrix composites "ceramics/crystal," and porous ceramics based on lead-free sodium-lithium niobates (Na, Li)NbO3 and sodium-potassium niobates (Na, K)NbO3 compositions. The measurements of elastic, dielectric and piezoelectric parameters, as well as microstructural studies of experimental samples of lead-free porous piezoelectric ceramics and composites were performed. It was shown that the use of alkali metal niobates in the form of ceramic matrix composites and porous ceramics allows to increase the main functional parameters of these materials and makes them competitive with piezoceramics of the PZT system. The developed lead-free porous and composite materials have a unique combination of parameters and can be used for the manufacture of ultrasonic transducers and devices for a wide range of applications, including medical and nondestructive testing equipment. [ABSTRACT FROM AUTHOR]

Piezoelectric composites are a class of functional materials consisting of piezoelectric active materials and non-piezoelectric passive polymers, mechanically attached together to form different connectivities. These composites have several advantages compared to conventional piezoelectric ceramics and polymers, including improved electromechanical properties, mechanical flexibility and the ability to tailor properties by using several different connectivity patterns. These advantages have led to the improvement of overall transducer performance, such as transducer sensitivity and bandwidth, resulting in rapid implementation of piezoelectric composites in medical imaging ultrasounds and other acoustic transducers. Recently, new piezoelectric composite transducers have been developed with optimized composite components that have improved thermal stability and mechanical quality factors, making them promising candidates for high temperature, high power transducer applications, such as therapeutic ultrasound, high power ultrasonic wirebonding, high temperature non-destructive testing, and downhole energy harvesting. This paper will present recent developments of piezoelectric composite technology for high temperature and high power applications. The concerns and limitations of using piezoelectric composites will also be discussed, and the expected future research directions will be outlined.

Based on planar cymbal transducer array, a low frequency broadband submarine acoustic actuator is presented and analysed. Several kinds of prototype of cymbal transducer are fabricated, and the properties of this transducer are tested. Three prototypes of planar cymbal transducer array, with thickness <20 mm, used as acoustic actuator are built and tested. The measured transmitting voltage response of acoustic actuators are >130 dB re 1 μPa/V@1m and flat over the frequency range of 3-15 kHz. It is shown that this kind of acoustic actuator has thin, low frequency broadband; thus, it can be used as a high power submarine actuator with a working frequency <10 kHz. The experiment system of active control for attenuating acoustic reflection of underwater target is built and tested. The results show that the cymbal actuator acts as an active sound absorption device that can attenuate acoustic reflection on underwater target effectively. [ABSTRACT FROM AUTHOR]

Abstract: Domain switching in piezoelectric materials is caused by external loads such as electric field and stress that leads to non-linear behaviour. A study is carried out to compare the non-linear behaviour of 1–3 piezocomposites with different volume fractions and bulk piezoceramics. Experiments are conducted to measure the electrical displacement and strain on piezocomposites and bulk ceramics under high cyclic electrical loading and constant compressive prestress. A thermodynamically consistent uni-axial framework is developed to predict the nonlinear behaviour by combining the phenomenological and micromechanical techniques. Volume fractions of three distinct uni-axial variants (instead of six variants) are used as internal variables to describe the microscopic state of the material. In this model, the grain boundary effects are taken into account by introducing the back fields (electric field and stress) as non-linear kinematic hardening functions. An analytical model based on equivalent layered approach is used to calculate effective properties such as elastic, piezoelectric, and dielectric constants for different volume fractions of piezocomposites. The predicted effective properties are incorporated in the proposed uni-axial model and the dielectric hysteresis (electrical displacement versus electric field) as well as butterfly curves (strain versus electric field) are simulated. Comparison between the experiments and simulations show that this model can reproduce the characteristics of non-linear response. It is observed that the variation in fiber volume fraction and compressive stress has a significant influence on the response of the 1–3 piezocomposites. [Copyright &y& Elsevier]

Piezocomposites with 1-3 connectivity have been extensively used in medical imaging transducers and high-intensity focused ultrasound transducers, but most studies of 1-3 piezocomposites address medical imaging applications. The purpose of this study was to completely investigate 1-3 composites specifically for high-power ultrasonic transducer applications via a series of experimental analyses. PZT4-epoxy composite focused transducers with various aspect ratios and volume fractions were constructed in-house for the evaluation of the coupling factor, dielectric loss tangent, quality factor, bandwidth, acoustic impedance, and electroacoustic efficiency. The experimental analyses demonstrated that although the coupling factor of composite transducers was higher than that of the ceramic transducer, the composite transducers had a lower efficiency due to the high dielectric loss and high mechanical energy loss of the composites. In addition, the bandwidth and acoustic impedance of composite transducers were superior to the ceramic transducer. For the composite transducers, the efficiency and acoustic impedance were inversely proportional to the aspect ratio and linearly proportional to the volume fraction. The coupling of inter pillars that are too close to each other could cause a significant decrease in the efficiency of the composite transducer. With an appropriate design in terms of the aspect ratio, volume fraction, and PZT-pillar spacing, a high-efficiency composite high-intensity focused ultrasound transducer can be achieved. [ABSTRACT FROM PUBLISHER]

Composite piezoelectric ceramics are important materials for transducer applications in medical diagnostic devices and MEMS devices. In micrometer scale the material properties of piezopolymers or piezoceramics do not coincide with that of bulk materials. The present work is aimed at simulating the material properties of piezoceramics and piezo-polymer composite thin films in the micrometer scale and then to determine the piezo-composite material properties. Piezoceramics have very high electromechanical coupling coefficient ( k). But they have very high acoustic impedance and they are very brittle especially when thin films are fabricated. Piezopolymer like PVDF has low acoustic impedance and can be fabricated into thin films but it has very low k value and high dielectric losses. The combination of piezoceramics and piezopolymers form the piezocomposites, which have suitable material properties for transducer applications. The composites can have different connectivities. For 2-2 composite, we can select two layers or a stack of PZT and PVDF layers. It is intended to determine the material properties both analytically and by simulation using computer simulation ANSYS software which implements finite element method (FEM). Although the simulation process presents approximate results, it can be verified from the large available experimental data from the literature with the simulated data. [ABSTRACT FROM AUTHOR]

This paper addresses the analysis of active constrained layer damping (ACLD) of geometrically nonlinear transient vibrations of laminated thin composite cylindrical shallow shells using vertically reinforced 1-3 piezoelectric composite (PZC). The constraining layer of the ACLD treatment is considered to be made of this 1-3 PZC material. The Golla-Hughes-McTavish (GHM) method has been implemented to model the constrained viscoelastic layer of the ACLD treatment in time domain. The Von Kármán type non-linear strain displacement relations and the first-order shear deformation theory (FSDT) are used for deriving this electromechanical coupled problem. A three dimensional finite element (FE) model of smart composite shallow shells integrated with a patch of such ACLD treatment has been developed to demonstrate the performance of the patch on enhancing the damping characteristics of thin laminated cylindrical shells, in controlling the geometrically nonlinear transient vibrations. The numerical results indicate that the ACLD patch significantly improves the damping characteristics of the shells for suppressing the geometrically nonlinear transient vibrations of the shells. The effect of variation of fiber orientation in the PZC material on the control authority of the ACLD patch has also been investigated. [ABSTRACT FROM AUTHOR]

This research employs solid-state actuators for delay of flow separation seen in airfoils at low Reynolds numbers. The flow control technique investigated here is aimed for a variable camber airfoil that employs two active surfaces and a single four-bar (box) mechanism as the internal structure. To reduce separation, periodic excitation to the flow around the leading edge of the airfoil is induced by a total of nine piezocomposite actuated clamped-free unimorph benders distributed in the spanwise direction. An electromechanical model is employed to design an actuator capable of high deformations at the desired frequency for lift improvement at post-stall angles. The optimum spanwise distribution of excitation for increasing lift coefficient is identified experimentally in the wind tunnel. A 3D (non-uniform) excitation distribution achieved higher lift enhancement in the post-stall region with lower power consumption when compared to the 2D (uniform) excitation distribution. A lift coefficient increase of 18.4% is achieved with the identified non-uniform excitation mode at the bender resonance frequency of 125 Hz, the flow velocity of 5 m/s and at the reduced frequency of 3.78. The maximum lift (Clmax) is increased 5.2% from the baseline. The total power consumption of the flow control technique is 639 mWRMS. [ABSTRACT FROM AUTHOR]

Abstract 0-3 and 1-3 composites were fabricated using piezoelectric single crystals (PSCs). These two connectivities were specifically chosen for large area fabrication. In particular, a lamination technique was used for 1-3 piezocomposites instead of the standard ‘dice and fill’ method. For 0-3 connectivity, the thickness coupling factor of the fabricated materials using PSC phase was twice that obtained using standard PZT powder for the same volume fraction (60%). However, the efficiency of the poling remained low. For the 1-3 piezocomposites, the properties (such as the thickness coupling factor which reached 74%) of the samples fabricated by the lamination technique were comparable to those obtained with standard methods. Finally, three ultrasonic transducers with centre frequencies between 600 and 850 kHz were fabricated to evaluate the performance of these new piezoelectric composites. [ABSTRACT FROM AUTHOR]

Abstract: 0-3 and 1-3 composites have been fabricated using piezoelectric single crystals (PSCs). These two connectivities were specifically chosen for large area fabrication. In particular, a lamination technique was used for 1-3 piezocomposites instead of the standard dice and fill method. For 0-3 connectivity, the thickness coupling factor of fabricated materials using PSC phase is twice the value obtained using standard PZT powder for the same volume fraction (60%). But the efficiency of the poling stays low. For the 1-3 piezocomposites, the properties (such as the thickness coupling factor) of the samples fabricated by the lamination technique are comparable to those obtained with standard methods. Finally, three ultrasonic transducers with center frequency between 600 and 850 kHz were fabricated to evaluate the performance of these new piezoelectric composites. [Copyright &y& Elsevier]

• Ultrasonic physiotherapy requires appropriate doses applied at the target body structure. • Array transducers made with piezocomposites show good focused diffraction pattern despite the spurious lateral and structural resonance modes. • New devices with array transducers with mechanical and electronic steering are needed to correctly apply Ultrasound Physioytherapy. Despite many years of clinical use of ultrasound, the results of different reviews of controlled trials on the efficacy of ultrasound physical therapy for different musculoskeletal injuries continue to question its efficacy. However, "in vitro" experiments with well-controlled cell cultures and experiments with animal models show positive results. The question is whether the commercial systems used by physiotherapists can deliver the required ultrasonic dose to the exact location on the body. The object of this work is the design, realization and testing of a new concept of ultrasound system for Physiotherapy capable of focusing the ultrasound beam to apply the required ultrasonic energy dose at the point targeted by the physiotherapist. The system is designed for non-thermal effects Physiotherapy. The system consists of conceptually new piezocomposite arrays with a metallic delay line, multi-pulser electronics for emission focusing, parallel robots for mechanical steering and positioning of the array transducers, and linear and angular encoders to allow the physiotherapist to direct the focus to the target. The multi-pulser and parallel robot angulation are controlled by the computer, using a graphical interface software. [ABSTRACT FROM AUTHOR]

Abstract: This paper addresses the analysis of active constrained layer damping (ACLD) of geometrically nonlinear transient vibrations of laminated thin composite plates using piezoelectric fiber-reinforced composite (PFRC) materials. The constraining layer of the ACLD treatment is considered to be made of the PFRC materials. The Golla–Hughes–McTavish (GHM) method has been used to model the constrained viscoelastic layer of the ACLD treatment in the time domain. A finite element model has been developed for the cross-ply and antisymmetric angle-ply plates integrated with the patches of ACLD treatment undergoing geometrically nonlinear vibrations. The Von Ka`rma`n-type nonlinear strain displacement relations and the first-order shear deformation theory (FSDT) are used for deriving this coupled electromechanical nonlinear finite element model. The numerical results indicate that the ACLD patches significantly improve the damping characteristics of the cross-ply and antisymmetric angle-ply plates for suppressing the geometrically nonlinear transient vibrations of the plates. Emphasis has also been placed on investigating the effect of variation of fiber orientation in the PFRC material on the control authority of the ACLD patches. [Copyright &y& Elsevier]

Abstract: Piezocomposite ultasonic transducers for high-frequency microelectronics wire bonding have been developed to alleviate the intrinsic mode coupling and high mechanical quality factor (Q m) in piezoceramic transducers. In this paper, a 136kHz transducer fabricated using lead zirconate titanate (PZT)/epoxy 1–3 piezocomposite rings with 77μm epoxy width and 0.89 PZT volume fraction is presented, together with a PZT piezoceramic transducer of similar structure. With the guide of a finite-element modal analysis, the nature of most experimental resonance modes in the transducers is identified. The low lateral coupling of the composite rings effectively suppresses the non-axial and many other spurious resonances in the composite transducer, retaining only the axial-mode resonances. Due to the effect of epoxy damping, the composite transducer exhibits a 2.4-times reduction in Q m to a desired low value of 296. This transducer has good potential to be used in commercial wire bonders for enabling high-frequency wire-bonding technology. [Copyright &y& Elsevier]

Abstract: This paper presents a mathematical modelling and numerical simulation method for three-dimensional smart tubular 1(0)-3 composites based on a representative composite volume (RCV) approach. For the problems we consider, numerical results show that the maximum mechanical displacement varies linearly with the applied electrical potential and grows nonlinearly with increasing the RCV height. Further, we observe that decreasing the distance between the inner and outer radii results in increasing the maximum displacement. This refers to composites with large Young’s modulus of the polymer phase, whereas for “soft” polymers (i.e. for Young’s modulus of the polymers of order less than GPa) no particular ‘rule’ is evident, in which case the Poisson’s ratio is the most important parameter. [Copyright &y& Elsevier]

This paper develops a theoretical electroelastic fracture mechanics for piezoelectric layered composites. A piezoelectric layer bonded between two elastic or piezoelectric materials containing a crack normal to the interfaces is considered. The ends of the crack are situated at equal distances away from the interfaces. Both analytical and simulation methods are formulated to determine the effects of applied electric field and polarization switching on the fracture mechanics parameters such as stress intensity factor, energy release rate, and energy density factor. The results for the exact (permeable) and approximate (impermeable) boundary conditions are presented in graphical form. [ABSTRACT FROM AUTHOR]

The acoustic characteristics of dense and porous piezoceramic disc hydrophones have been studied by finite element modelling (FEM). The FEM results are validated initially by an analytical model for a simple disc of dense piezoceramic material and then it is extended to a porous piezoceramic disc replicating a foam-reticulated sample. Axisymmetric model was used for dense piezoceramic hydrophone due its regular geometric shape. 3-dimensional model was used for the porous piezoceramics, since the unit cell model is inadequate to fully represent transducers of finite lateral dimensions. The porous PZT discs have been synthesised by foam-reticulation technique. The electrical impedance and the receiving sensitivity of the hydrophones in water are evaluated in the frequency range 10–100 kHz. The model results are compared with the experimental data. The receiving sensitivity of piezocomposite hydrophones is found to be reasonably constant over the frequency range studied. The sharp resonance peaks observed for the dense piezoceramic hydrophone has broadened to a large extent for porous piezoceramic hydrophones, indicating higher losses. The flat frequency response suggests that the 3–3 piezocomposites are useful for wide-band hydrophone applications. [Copyright &y& Elsevier]

In this paper a Euler–Bernoulli-like model of layered piezoelectric beams is presented. It describes more accurately than the others already presented in the literature both transverse (Poisson and piezoelectrically induced) cross-sectional deformations and through-the-thickness variations of the electric field and electric displacement. A deductive approach based on a mixed variational formulation is adopted and distributions of deformation, stress, electric field and electric displacement are simultaneously prescribed. The attention is focused on the choice of the most fitting assumptions to recover complex 3D cross-sectional field distributions. In particular, transverse interactions between different layers are taken into account by enforcing specific conditions on transverse stress through the Lagrange multipliers method. The estimate of electromechanical beam constitutive coefficients is discussed and comparison with standard modelling approaches, which assume either vanishing transverse stresses or vanishing transverse strains, is emphasized. For a sandwich piezoelectric beam and for a two-layer beam, expressions of the beam constitutive coefficients are provided and the main features of the proposed model are highlighted by presenting the through-the-thickness distribution of the 3D state fields associated to beam-axis deformations and applied voltage. As a main peculiarity, the proposed beam model is able to coherently estimate the equivalent piezoelectric capacitance also when the thickness of elastic and piezoelectric layers is comparable. [Copyright &y& Elsevier]

The transducer characteristics of hydrophones manufactured from porous 3–3 piezocomposites are compared with dense piezoceramic disc hydrophones using finite element modelling. Due to the complex porous structure of the 3–3 piezocomposites, a real-size 3-dimensional model was developed while a 2-dimensional axisymmetric model was constructed for the simple dense disc hydrophone. The electrical impedance and receiving sensitivity of the hydrophones in water were evaluated in the frequency range 10–100 kHz. The model results were compared with the experimental results. The sharp resonance peaks observed for the dense piezoceramic hydrophone were broadened to a large extent for porous piezocomposite hydrophones due to weaker coupling of the structure. The receiving sensitivity of piezocomposite hydrophones is found to be constant over the frequency range studied. The flat frequency response suggests that the 3–3 piezocomposites are useful for wide-band hydrophone applications. [Copyright &y& Elsevier]

A 3 × 3 hydrophone array for low frequency applications was constructed from reticulated PZT ceramic foams. The hydrophone array was tested for receiving sensitivity and compared with single element PZT-air and dense PZT hydrophones. The composite array showed a flat response in the 20 kHz–100 kHz frequency range while the single element hydrophone displayed broadening radial resonance around 50 kHz. The flat, broadband response indicates that the radial resonance is suppressed by both porous nature of the PZT-air composites and the array construction of the hydrophone. The sensitivity of the array hydrophone was –205 dB re 1 Vμ Pa-1. [ABSTRACT FROM AUTHOR]

Ultrasonic transducers made with 1–3 connectivity piezocomposites are frequently used in Medical applications and nondestructive testing. When the transducer is used for special applications as, for instance air-coupled transmission, it is necessary to compensate for the high difference of acoustic impedance between transducer and medium using high amplitude pulses to generate high acoustic signal. Thus, the nonlinear behavior of the transducer must be taken into account in similar application conditions. The newly developed method, which performs the nonlinear characterization with burst signal excitation near the thickness resonance frequency, is based on the measure of the current as well as the vibration velocity of the piezocomposite transducer. The current of the stationary response is measured before the end of the burst signal excitation. Burst excitation enables us to measure the nonlinear characterization without producing overheating in the transducers. The amplitude level dependence of mechanical losses tanδm and the stiffness increases |Δc/c0| have been studied, as well as the velocity dependence of a point of the transducer, measured with a laser vibrometer. In this method, the power level applied to the transducers can be higher than other nonlinear measurement methods, providing measurements of high accuracy. [Copyright &y& Elsevier]

The processing of novel 2-2 and 3-3 PZT ceramic-polymer composites with various orientation of the ceramic phase with respect to the poling direction is presented. The volume fraction of the ceramic was chosen to be 30 percent for both types of composites. The orientation angle (θ) of the ceramic phase varied between 0° and 75° for both types of composites with 15° increments. The ceramic structures were fabricated using one of the Solid Freeform Fabrication (SFF) methods, particularly Fused Deposition of Ceramics (FDC). The sintered structures were embedded in hard epoxy and the effect of orientation angle on the electrical properties of the composites was evaluated. By increasing the orientation angle of the ceramic phase, the dielectric constant and the piezoelectric strain coefficient of both types of composites decreased. Although the piezoelectric voltage coefficient of the 2-2 composites showed a minor improvement with increasing θ at 45°, the g33 value of the 3-3 composites increased considerably with θ and reached 80 mV/N at θ = 45°. Further increase of the orientation angle reduced the g33 of such composites. [ABSTRACT FROM AUTHOR]

The effective material parameters of the 3-3 piezocomposites are estimated using constitutive equations corresponding to the thickness-mode oscillations of a piezocomposite plate resonator. The dielectric constant (ℇ 33 T / ℇ 0 ), piezoelectric coefficients (d 33 , d 31 , d h , g h and e 33 ), stiffness coefficient ( c 33 E ), electrical impedance spectrum, electromechanical thickness-mode coupling coefficient (k t ), acoustic impedance (Z aco ) of the 3-3 composites are evaluated as a function of piezoceramic/polymer volume fraction. The results are compared with the experimental data. [ABSTRACT FROM AUTHOR]

High power resonant transducers made with 1-3 piezocomposites are widely used in Non Destructive Testing (NDT) for industry and ultrasonic medical devices. A new nonlinear characterization method with burst excitation, in similar conditions to those in air-transducer applications, is proposed. It measures both the current flowing and the vibration velocity in the piezocomposite transducers, just before the end of the burst signal excitation, near the thickness resonance frequency for different piezocomposites. Three amplitude level dependencies have been studied: a) mechanical loss tangent tan δ m , b) the stiffness variations Δ c / c 0 and c) the ratio between velocity and current. This method allows us to characterize accurately the nonlinearity of piezocomposites as well as ceramics of low or high mechanical quality factor, avoiding the overheating of the transducer. [ABSTRACT FROM AUTHOR]