Elastic and piezoelectric properties of piezoelectric composite materials
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Abstract
This paper offers theoretical and experimental examinations of the elastic and piezoelectric properties of piezoelectric composite materials used mainly for ultrasonic medical-diagnosis apparatus. One-dimensional multilayer composite materials in which the thickness of each layer is less than the wavelength of elastic waves (i.e., each layer can be regarded as uniform), were analyzed rigorously, and their equivalent elastic, piezoelectric, and dielectric constants were obtained. By using the results, the characteristics of a vibrator employing the one-dimensional composite-material (piezoelectric ceramic and epoxy resin) were examined. the relationship between the high-coupling and low-impedance (which are the features of this type of composite material) and the behavior of each component material was investigated. A model which evaluates the characteristics of the 1-3 type twodimensional composite piezoelectric material (which is important for practical ultrasonic transducers) was proposed. the characteristics of a vibrator made of this material were examined. Not only can this model explain the known experimental facts, but it can easily deduce the piezoelectric constants which are important for evaluating the spurious response. A vibrator using the composite material was fabricated. Its characteristics agree reasonably well with the result of the analysis. the proposed method can be expanded for composite materials other than the 1-3 type, and will be useful for the design and development of general compound materials.