Evaluation of piezocomposites for ultrasonic transducerapplications influence of the unit cell dimensions and the properties ofconstituents on the performance of 2-2 piezocomposites

摘要

A theoretical model on piezoceramic polymer composites withnlaminar periodic structure is presented. A salient feature of this modelnis that it can treat explicitly how the unit cell dimensions and othernmaterial properties influence the performance of an ultrasonicntransducer made of 2-2 piezocomposites. The model predicts that therenexist a series of modes associated with the periodic structure of ancomposite, which is beyond the stop-band edge resonance prediction. Onenof the main concerns in designing a composite transducer is how thensurface vibration profile changes with frequency and how this isninfluenced by the aspect ratio of the ceramic plate. It was predictednthat as long as the thickness resonance is below the first lateral modenfrequency, there is always a frequency f1 which is near thenthickness resonance and at which the polymer and ceramic vibrate innunison. The effect of aspect ratio is to change the position of f1n with respect to the thickness resonance frequency and thenbandwidth in which polymer and ceramic have nearly the same vibrationnamplitude and phase. It is also predicted that, when operated in a fluidnmedium such as water, there will be a resonance mode which has anfrequency determined by the velocity of the fluid medium and the unitncell length d and is associated with the oscillation of the fluid. Thenbehavior of a composite plate as an acoustic transmitter and receivernand the influence of the aspect ratio of the ceramic plate on them arenalso investigated