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A systematic investigation of the stress-dependent non-linear electromechanical properties of 1-3 piezocomposites for different fiber volume fractions and bulk piezoceramics is carried out. Experiments are conducted to measure the electrical displacement and longitudinal strain on piezocomposites and bulk ceramics under uni-axial compressive stress loading conditions. A simplified uni-axial micro-macromechanical model based on thermodynamic framework is developed to predict the behaviour. 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 order to calculate the effective properties (elastic, piezoelectric and dielectric constants) of piezocomposites for different fiber volume fractions, an analytical model based on equivalent layered approach is proposed. The predicted effective properties are incorporated into uni-axial model and the classical stress versus strain and stress versus electrical displacement curves are simulated. Comparison between the experiments and simulations show that the proposed model can reproduce the characteristics of non-linear coupled response. It is observed that, the variation in the fiber volume fraction has a significant influence in the response of 1-3 piezocomposites. � 2012 Elsevier Masson SAS. All rights reserved.

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 ceramics under high cyclic electrical loading. A thermodynamically consistent framework, combining the phenomenological and micromechanical models, is developed to predict the coupled behavior. 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. In order to calculate the effective properties (elastic, piezoelectric, and dielectric constants) of piezocomposites for different volume fractions, an analytical model based on equivalent layered approach is proposed. The predicted effective properties are incorporated in the proposed model, and the classical hysteresis (electrical displacement versus electric field) as well as butterfly curves (strain versus electric field) is simulated. Comparison between the experiments and the simulations shows that this model can reproduce the characteristics of non-linear coupled response. It is observed that the variation in fiber volume fraction has a significant influence on the response of the 1-3 piezocomposites. � 2012 American Institute of Physics.

An analytical method based on parallel and series models is developed to evaluate the performance of 1-3 piezoelectric composite where both matrix and fiber phases are piezoelectrically active. A parametric study is conducted to investigate the influence of the volume fraction of ceramic on the smart composite and the performance of the 1-3 composite for underwater acoustics and biomedical imaging has been addressed. The present model is capable of predicting the effective properties of the composite subjected to thermo-electro-mechanical loading conditions. Simulated results are compared with experimentally measured data reported in literature (Taunaumang et al., 1994 [1]) and are found to be in reasonable agreement. The outcome of the present study demonstrates the influence of thermal effect on effective properties of the composite induces the polarization in the composite. Along the loading direction, there is a significant reduction in the effective pyroelectric coefficient of the piezocomposites, except near the monolithic ceramic fiber material. � 2010 Elsevier B.V. All rights reserved.

This work focuses on evaluating the time-dependent non-linear ferroelastic behaviour of 1-3 piezocomposites under pure uni-axial compressive stress loading condition. An experimental setup is developed to study the influence of high-stress levels on the stress-strain and stress-polarization behaviour of 1-3 piezocomposites. The electro-elastic effective properties of 1-3 piezocomposites are measured experimentally based on IEEE standard and compared with the proposed numerical model using finite-element software ABAQUS. The time-dependent effective properties are evaluated using viscoelastic model and it is incorporated into a 3D micromechanical model to predict the viscoelastic behaviour of 1-3 piezocomposites under mechanical loading. The simulated results are compared with the viscoelastic behaviour of 1-3 piezocomposites obtained from experiments. � 2015 Author(s).

Non disponible / Not available, La stéréolithographie (SPL) est un procédé de prototypage rapide, basé sur la photopolymérisation d'un monomère liquide en un polymère solide à l'aide d'un faisceau laser. Cette technique de prototypage rapide a été mise en oeuvre dans le but de fabriquer des composites polymère/céramiques piézoélectriques (PZT). La caractérisation des propriétés rhéologiques et photochimiques des suspensions a conduit au choix de deux formulations compatibles avec le procédé de SPL. Leur emploi est fonction de leur charge massique en céramique qui varie de 50 à 85%. Ces expériences ont également montré que les dispersions de PZT absorbaient fortement le rayonnement UV, ce qui implique de faibles épaisseurs polymérisées. De plus, l'influence de l'oxygène sur la résolution du procédé de SPL a été mise en évidence. Par conséquent, une modification du procédé a été nécessaire afin de réduire l'épaisseur de couche déposée à 10[micro]m, dans le but d'assurer une bonne cohésion des objets. Dans cette optique, un nouveau système de déposition de couches de céramiques, constitué d'une buse d'injection d'azote, a été développé. Par ailleurs, l'ensemble du procédé de SPL a été transformé afin de permettre la mise en forme de céramiques piézoélectriques. Grâce à ces améliorations, des films épais de PZT, des piézocomposites 1-3 et d'autres pièces fortement chargées en céramiques fonctionnelles ont été réalisées. La mise en forme par SPL est suivie d'un traitement thermique durant lequel le polymère est éliminé. Des mesures ont montré que les échantillons frittés possédaient des densités voisines de 96% de la densité théorique. Enfin, les céramiques ont été métallisées puis polarisées afin d'étudier leurs propriétés ferroélectriques et piézoélectriques. Ces analyses ont démontré la fonctionnalité des zircono-titanates de plomb fabriqués par SPL et leur intégration possible au sein de microsystèmes (MEMS). Les applications couvertes par ce type d'objets sont nombreuses et vont du microactionneur au capteur. . .

A micromechanics-based analytical model is developed to evaluate the performance of 1-3-2 piezoelectric composite where both matrix and fiber materials are piezoelectrically active. A parametric study is conducted to investigate the influence of the ceramic base and the fiber volume fraction on the modified 1-3 composite. The performance of the 1-3-2 composite as a transducer for underwater acoustics and biomedical imaging applications has been analyzed. The proposed model is capable of predicting the effective properties of the composite subjected to thermoelectromechanical loading conditions. Simulated results of 1-3 type piezocomposite compare well with experimentally measured data reported in the literature (Taunaumang et al 1994 J. Appl. Phys. 76 484-9). The present study demonstrates that the low end ceramic base volume fraction of 1-3-2 composite yields comparative performance with 1-3 type composite. It is observed that the influence of thermal effects on the effective properties of the composite also induces the polarization in the composite. � 2010 IOP Publishing Ltd.

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.

Summarization: A mathematical model of smart composite beams and plates with piezoelectric layers that take into account the adhesive between the layers has been created. The finite element method has been used for the numerical solution of related static and dynamic problems. Furthermore, delamination between various layers has been modelled, in order to estimate one of the most commonly appearing damage in composites. Finally, active control is applied by means of optimally tuned fuzzy inference rules. Tuning has been achieved using genetic optimization. The results demonstrate a viable way of modelling and optimal design of active smart piezocomposites. Παρουσιάστηκε στο: 3rd Polish Congress of Mechanics, PCM 2015 and 21st International Conference on Computer Methods in Mechanics