Construction and evaluation of a new generation of flexible ultrasonic transducers

This paper describes the construction of a new generation of flexible ultrasonic transducers. The device consists of an array of piezoceramic platelet devices of high aspect ratio embedded within a soft polymer matrix, supported by a copper/polyimide flexible printed circuit board. Theoretical modelling using both a linear systems approach and the ANSYS finite element package was used to predict transducer behaviour, and compared with experimental results and surface displacement profiles with good correlation. In addition, the linear systems technique was utilised to evaluate potential piezoceramic materials and the results compared to a conventional thin piezopolymer film transducer structure. The ceramic/polymer platelet transducer has been implemented in two application areas: a 6 MHz multi-element linear array for flaw detection in curved test specimens, allowing imaging of test piece construction; and efficient generation of the fundamental symmetrical Lamb wave at frequencies below 500 kHz, using interdigital design techniques, in both aluminium and carbon-fibre reinforced polymer composite plates. Experimental results will be presented which will demonstrate the application of this flexible transducer technology to practical NDE