Lifetime of piezoceramic multilayer actuators: Interplay of material properties and actuator design

We report an investigation into factors limiting the functional lifetime of multilayer piezoceramic actuators. The study consists of a combination of lifetime experiments by means of an accelerated lifetime test, inspection of the actuator microstructure at different stages of the accelerated lifetime test, and numerical simulation of the displacements and mechanical stresses that arise during actuator performance. During the lifetime test, both displacement and electrical properties were measured. The results show a clear correlation between the microstructure and the mechanical stresses in the actuator, giving evidence that crack initiation starts early in actuator lifetime and humidity effects accelerate degradation. The numerical simulations performed provide clues for optimization of the actuator design with respect to stress development and performance. Attention is paid to the choice of adhesive interlayer and its effect on the performance and lifetime of the actuator.