Pre-stressed Curved Actuators: Characterization and Modeling of their Piezoelectric Behavior

Pre-stressed curved actuators consist of a piezoelectric ceramic (lead zirconate titanate or PZT) sandwiched between various substrates and other top layers. The substrates used in this study are stainless steel, and fiberglass. The top layers are made up of aluminum and carbon. Due to their enhanced strain capabilities, these pre-stressed piezoelectric devices are of interest in a variety of aerospace applications. Their performance as a function of electric field, temperature and frequency is needed in order to optimize their operation. During the processing steps, a mismatch between the properties of the various layers leads to pre-stressing of the PZT layer. These internal stresses, combined with restricted lateral motion, are shown to enhance the axial displacement. The goal is to gain an understanding of the resulting piezoelectric behavior over a range of voltages, and frequencies, for unloaded conditions. To quantify the relationship between the state of stress in the ceramic and the overall performance, a physics-based model is developed incorporating both thermo elastic relations and ferroelectric domain theory. The model predicts displacements based on the geometry and physical characteristics of the actuator components. The accuracy of the model and associated numerical method is demonstrated through comparison with experimental data for various input voltages, and boundary conditions.