Designing for piezoelectric ceramic wafers bonded on structures using force transfer criteria

Piezoelectric ceramic wafers embedded or surface mounted are able to generate transverse forces to control structural shape and vibration. These actuators are excited by applying an electric field through the thickness of the piezoelectric ceramic wafer. The proper design of their dimensions such as wafer thickness, and applied actuation voltage will enhance the system reliability, and guarantee the optimal control authority. This paper shows that the force transfer from the piezoelectric ceramic wafer to the structure, rather than the shear stress transfer in bond lines, becomes a key issue in the design when the length relative to the thickness of the piezoelectric ceramic wafer is large. It should be noted at this point that the shear stress distribution in the bond lines may influence the durability of the piezoelectric ceramic actuation system and, therefore, should also be considered when designing the system as a whole. This aspect of design is not discussed here. The force transfer is basically determined by the force transfer efficiency and block force in association with the wafer thickness. Therefore, this paper presents a design window for piezoelectric ceramic wafers bonded onto structures that is based on the relations between the force transfer and the wafer thickness, and also accounting for the applied actuation voltage and dielectric breakdown voltage of the piezoelectric material. The design window clearly describes the upper bound of the force transfer and the maximum value that can be achieved. It is also used to find an appropriate wafer thickness and actuation voltage when a minimum value of force transfer is required. In addition, an analytical model is developed in order to express the relation between the force transfer and the wafer thickness. This model is compared to the results from finite-element analysis. Limitations of the analytical model are described.