Mode coupling in lead zirconate titanate/epoxy 1-3 piezocomposite rings

Lead zirconate titanate (PZT)/epoxy 1-3 piezocomposite rings were fabricated with PZT volume fractions phi ranging from 0.82 to 0.94 and with a small epoxy width of 77 mum in order to investigate their resonance characteristics and to reveal the mode coupling. Four major resonance modes were observed, namely the coupled longitudinal-thickness f(H) and lateral f(L1) and f(L2) mode resonances of individual PZT elements inside the rings as well as the radial f(R) and wall-thickness f(W) mode resonances of the whole rings. No stopband resonances were observed in the frequency range of I to 10 MHz. f(H) was found to increase linearly with the decrease in element height while f(L1) and f(L2) remained constant. When the height and width of the elements became comparable, coupling of fH with f(L1) and f(L2) occurred. The observed f(H), f(L1), and f(L2) for all samples agreed with those calculated by the mode-coupling theory. f(R) and f(W) were almost independent of the ring thickness but increased as phi increased. A guide of operating f(H) in the rings without causing mode coupling was presented to optimize the composite structure for transducer design. (C) 2001 American Institute of Physics.