P2O-2 Exploring the Advantages of a Random 1-3 Connectivity Piezocomposite Structure Incorporating Piezoelectric Fibres as the Active Element

This paper describes the use of piezoelectric ceramic fibres (PZT5A) for the fabrication of 1-3 composite transducers. Importantly, extensive FE analysis, using the PZFlex code, of these devices has been undertaken with complete 3D models utilised to reflect the random nature of the device structure. The manufacturing process is based on the place-and-fill method. A fibre composite block is produced, from which it is then possible to slice a number of layers of piezoelectric material with a thickness corresponding to the desired frequency of operation. These layers have electrodes applied and are then poled. Electrical impedance profiles of each device demonstrate excellent unimodal behaviour at the thickness resonance frequency, and show excellent correspondence with the FE models. Moreover, these devices possess high electromechanical coupling coefficients (kt > 0.65) for a ceramic volume fraction of 50% and a medium-set polymer (CIBA GEIGY CY221-HY956). Laser vibrometry scans of transducer surface motion corroborate the FE predictions of average uniform surface displacement notwithstanding local variations due to the random nature of the microstructure. Experimental pulse-echo assessments, when operating into a water load, demonstrate comparable sensitivity and bandwidth characteristics between a random fibre and conventional 1-3 composite, with similar specification