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Analysis of piezoelectric cylindrical actuators and 1-3 piezocomposite unit cells Chen, Yue

Abstract

Adaptive structures incorporated with sensors and actuators are increasingly used in many engineering applications. Actuators used in adaptive structures are made out of piezoelectric ceramics, shape memory alloys (SMA), electrorheological fluids (ER fluids) or magnetostrictive materials. Among the many types of piezoelectric actuator elements, the cylindrical shape is widely used in practical applications involving fuel injectors, atomic force microscopes, high-precision telescopes, etc. In addition, the piezoelectric phase of piezocomposites is made out of cylindrical rods or fibers. Piezoelectric materials are very brittle and stress/electric field concentration at electrodes and other discontinuities often contribute to mechanical or dielectric breakdown. The study of electromechanical field of a cylindrical piezoelectric element and a composite unit cell with a piezoceramic core surrounded by a polymeric shell is therefore important to the understanding of failure of cylindrical actuators and design of piezocomposites for maximum electromechanical coupling. This thesis presents a comprehensive theoretical study of homogeneous piezoelectric cylinders and a unit cell of 1-3 piezocomposites. The governing equations for coupled axisymmetric electroelastic field in a transversely isotropic piezoelectric medium are established in terms of the displacements and electric potential. The general solutions of the governing equations are obtained in terms of a series of Bessel functions of the first and second kind. Several boundary-value problems are solved, and a computer code is developed to compute the electroelastic field in solid and annular cylinders for different aspect ratios, electromechanical loading and material properties. The salient features of the electroelastic field are identified. The effective properties of a 1-3 piezocomposite are studied under hydrostatic loading for different fiber volume fractions and polymer and ceramic properties. Optimum fiber volume fractions for maximum electromechanical coupling are determined for different ceramic-polymer combinations.

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