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Polymer Piezoelectric Transducers for ultrasonic NDE

POLYMER PIEZOELECTRIC TRANSDUCERS FOR ULTRASONIC NDE POLYMER PIEZOELECTRIC TRANSDUCERS FOR ULTRASONIC NDE Yoseph Bar-Cohen, Tianji Xue and Shyh-Shiuh Lih Excitation of ultrasonic waves can be done by numerous methods that induce time-dependent elastic deformation or pressure whereas receiving such waves requires means of converting time dependent displacements to an electric signal. Since piezoelectric crystals are offering a low cost, highly effective actuator/sensor materials they remained for many years the leading form of ultrasonic transduction. The most widely used commercial piezoelectric material is the various phases of lead zirconate titanate (PZT). Unfortunately, ceramic transducers are fragile and it is very difficult to produce them in large sizes. Further, these piezoelectric materials have a relatively high acoustic impedance requiring a complex damping and matching techniques to induce broadband signals. Polymer piezoelectric materials have been known to exist since the end of the twenties but the discovery of Polyvinylidene Fluoride, during the sixties, made them useful for commercial ultrasonic transducer applications. Piezoelectric polymers are associated with a low noise and inherent damping that makes them very effective receivers as well as broadband transmitters for high frequencies tasks. This paper reviews polymer piezoelectric materials, the origin of their piezoelectric behavior and their applications to ultrasonic NDE.

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