Characters Of Functionally Graded Piezoelectric Smart Beams And Their Applications

Piezoelectric material has been known as low-cost, lightweight, and easy-to-implement material which may be used in next generational structures -- smart structures. In order to gain high control forces, multilayered piezoelectric actuators are designed. However, due to the fact that the bonding layer in traditional multilayered devices may crack at low temperature or peel off at high temperature, which will reduce the lifetime and reliability of these piezoelectric devices. Moreover, conventional layered piezoelectric actuators suffer heavily from high stress concentration near the interlayer surfaces because of the abrupt changes in both their material composition and properties, which can cause severe deterioration in both the interlayer bonding strength and the response performance. For above reasons, more and more sensors and actuators have been designed with graded properties. Functionally graded piezoelectric materials (FGPM), comprising a new class of smart composite materials, have received more and more attention since they were proposed. It is hoped that the mechanical stresses can be significantly reduced or eliminated in FGPM structures.A lots of problems must be solved for functionally graded piezoelectric materials can be used in enginecring. For example, exact analytical models and effective numerical methods are expected. The present works include: 1) an exact solution for a functionally graded beam is obtained with the theory of elastic and a discussion of design considerations and optimization of device performance is presented by using this solution; 2) analytical solutions for some typical multilayered structures are carried out with considering the effect of bonding layers or electrode layers on the performances of these structures; 3) the static bending, free vibration and dynamic response of a functionally graded piezoelectric beam are investigated under a combined thermal-electro-mechanical load utilizing differential quadrature method and Timoshenko beam theory which takes the effect of transverse shear deformation into account; 4) a new method for parameter identification of functionally graded piezoelectric materials is developed by appealing to above solutions; 5) a mechanics-based analytical model to address the interactions between a window and the noise field outside a room is developed with considering that the strategic importance of reducing noise is increasing, together with the importance of acoustic comfort inside buildings.In one word, the present investigation will be expected to perfect the theory and analytical method for functionally graded materials, and to provide a guidance for design considerations and applications of functionally graded piezoelectric smart structures.