For the development of optimised health monitoring systems and smart materials, the understanding of the interaction of piezoelectric transmitting and receiving transducers with the structure is essential. This paper reports on the development of an experimental technique to determine the acousto-ultrasonic transfer characteristics of adhesively bonded piezoceramic transducers. Five millimeter diameter piezoceramic discs with and without brass backing were glued to one and two millimeter thick aluminium plates. Narrow and broad band excitation pulses were applied to the transducers in a frequency range between 50 kHz and 1 MHz, a frequency regime suitable for guided wave ultrasonic non-destructive evaluation applications. The electro-mechanical transfer properties of the ultrasonic transmitter elements were determined using a heterodyne Doppler laser vibrometer as a noncontact receiver device and Rayleigh-Lamb wave theory to describe the propagation behaviour of the waves in the structure. It is found that the transfer characteristics are extremely complex including sharp and narrow as well as broader but less pronounced frequency regimes of high energy transfer. It is shown that the major features of the transfer functions for different experimental configurations are similar, but the magnitudes of the peaks and their locations in frequency space are different for individual transducer/substrate combinations.
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