DETERMINATION OF YOUNGS MODULUS OF THE REDUCED LAYER OF A PIEZOELECTRIC RAINBOW ACTUATOR

The reduced and internally biased oxide wafer (RAINBOW) actuator, a ne w type of monolithic piezoelectric bending device, is composed of a re duced electromechanically passive layer and an unreduced piezoelectric layer. The determination of the elastic properties of the reduced lay er is important for optimizing actuator performance. In this paper, an analytical expression for bending resonant frequency is derived for t he cantilever RAINBOW actuator by using composite beam theory. A reson ance method is then described for determining Young's modulus of the r educed layer of RAINBOW actuator. As a piezoelectric bending actuator, RAINBOW can be excited by its electromechanically active PZT layer wi thout using any external excitation method. Young's modulus can be cal culated by measuring its resonant frequency, sample geometry, and dens ities of component parts. For comparison, the Young's modulus is also determined by measuring the resonant frequency of a completely reduced plate with an external acoustic excitation method. The results obtain ed by these two excitation methods show good agreement. (C) 1998 Ameri can Institute of Physics.