Effect of a middle layer on piezoelectric plate transformer

An additional middle elastic layer is considered between input and output portions in a piezoelectric plate transformer due to interface bonding glue possibly used excessively. A theoretical solution of thickness-shear modes is obtained to investigate the effect of the middle layer on the piezoelectric transformer. An examination of the numerical results demonstrates that the addition of middle layer would reduce the transforming ratio. Specifically, the increase of the thickness of the middle layer decreases the transforming ratio, whereas the middle layer´s elastic coefficient improves it oppositely. Furthermore, if the thickness of the middle layer vanishes small, the effect of the middle layer can be treated approximately as same as that of the imperfect interface by shear-slip model. Numerical example verifies that the difference between them is slightly small which can be ignored.