The effect of pillar misalignment on the underwater performance of high frequency multilayer 1-3 piezocomposite transducers with acoustic matching and backing layers

This paper reports 2-layer piezocomposite elements for high-density arrays operating in the 1-5 MHz range. Investigation in air without any ancillary acoustic components highlighted undesirable effects, showing that pillar misalignment led to extraneous twisting modes. In practical use, such elements include matching and backing layers, and the effects of acoustic loading must also be considered. Therefore, we report here on work to quantify the influence of pillar misalignment for a complete transducer operating in water. To evaluate performance, our analysis includes electrical impedance data and measurements of the transmit-receive transfer function which relates to device performance in practical situations. We present results from finite element analysis incorporating unidirectional and bidirectional pillar misalignments from 0% to the maximum possible. These results are validated with data from a prototype two-layer 1-3 piezocomposite transducer tested in air and underwater. We comment on the degree of acceptable pillar misalignment compared with previous studies.