Investigation of fracture properties of a piezoelectric stack actuator using the digital image correlation technique

Abstract

In this study, the fracture properties of a piezoelectric stack actuator made of a single crystal (PMN-29PT) were investigated using a three point bending test along with the digital image correlation (DIC) technique. To simplify the model of the piezoelectric stack and minimize the cost, two layers of PMN-29PT and one thin copper electrode were glued together using silver conductive adhesive instead of a real piezoelectric stack with 40PMN-29PT layers. The PMN-29PT layers were then strongly attached with a two square section acrylic beam forming a beam with the same geometry as the piezoelectric stack. The three point bending test results showed that the force at the crack onset was around 85% of the fracture force. The maximum stress and fracture energy from force-displacement data were measured to be 1.41MPa and 3.83J/m2, respectively. Furthermore, the fracture surface indicated that the fracture energy was affected by the surface of the copper electrode, and that the rough surface of the electrode can increase the fracture energy. The fracture energy was determined using a simple beam theory. The fracture energy according to the simple beam theory was slightly smaller than that from force-displacement data. Understanding the measured fracture properties of the piezoelectric stack will help us prevent the fracture of the stack when the piezoelectric stack actuator is handled.