Abstract
Piezoelectric actuators with functionally graded microstructure (FGM) are designed with the aim of reducing the stress concentration at the middle interface that exists in the standard bimorph actuators while maintaining high bending displacement. A FGM piezoelectric laminate consists of a number laminae, which are composite materials with electroelastic properties varied through the laminate thickness. The electroelastic behavior of piezo-actuators with laminated composite is studied by two-stage hierarchical model, the first based on the Eshelby’s model for predictions of the electroelastic properties of each lamina, the second based on classical lamination theory (CLT). The in-plane stresses and out-of-plane displacements are obtained by the CLT for both standard and FGM piezoelectric bimorph actuators under the assumption of cylindrical bending. The microstructure of the FGM biomorph actuator is optimized by using CLT model to achieve the best performance of the FGM piezoelectric actuator, i.e. large bending displacement while minimizing the induced stress field. Based on the optimized microstructure of the FGM bimorph actuators by the CLT model, we processed the FGM bimorph actuator that is composed of six laminae, and also the standard bimorph actuator. The bending displacements of these actuators are then measured by a laser displacement measurement apparatus as a function of applied voltage. The measured data of the bending displacements versus applied voltage are compared with the predictions by the CLT, resulting in a good agreement.