Numerical Stress Investigation for Piezoelectric Elements with a Circular Cross Section and Interdigitated Electrodes

The scientific community has put significant effort into the development and optimization of sensors and actuators manufactured as piezoelectric composites with interdigitated electrodes (IDEs), well known as active fiber composite (AFC) and macro fiber composite (MFC). The advantages of these elements are their higher actuation performance and flexibility as compared to monolithic piezoceramic (PZT) elements. In general, their mechanical properties are calculated based on the classical lamination theory and the uniform field model (UFM). These two theories are well suited for predicting the stiffness and piezoelectric strain constants of the AFC or MFC. Although there are a variety of numerical investigations related to their electromechanical properties, there are no appropriate tools for accessing the stresses within these piezoelectric elements (including the inhomogeneous electric field conditions as well as the change in material properties). Explanations are given for this situation indicating the problems in investigating these types of piezoelectric elements with respect to stress states. In this work a finite element modeling approach is presented, which shows the influence of the IDE on the mechanical properties of PZT fibers. Experimental evidence is presented, which affirms the location of critical stress predicted in this model and explains the reported cracking in AFC in past research.