Poling Process of Composite Piezoelectric Sensors for Structural Health Monitoring: A Pilot Comparative Study

Piezoelectric transducers are widely used as sensors and actuators, benefiting from their well-known smart asset of energy conversion. Synthesized piezoelectric materials, including thin/thick films and stacked wafers, are subject to a process, called poling, before implementation. The poling process significantly helps to resuscitate or enhance the piezoelectric properties of a deteriorated semi-isotropic structure by activating/energizing the dipoles. The poling process consists of exposing the piezoelectric films/wafers to high electric field to apply external energy to the granular structures and, thus, enhance the piezoelectric response. This article reports the results obtained during the poling process of composite piezoelectric films with different sizes and thicknesses, which are deposited on the curved surface of superalloy blades in order to conduct structural health monitoring. This article also studies effects of parameters such as poling temperature, applied electric field, polarizing time, porosity, and film size on electric, ferroelectric, and piezoelectric properties of different specimens. Experiments are conducted by controlling annealing time, temperature, and, thus, grain size, while nitrogen gas is blown into the tube furnace at the time the samples are thermally treated after deposition.