Durability and Survivability of Piezoelectric Wafer Active Sensors on Metallic Structure

Piezoelectricwaferactive sensorsare small, inexpensive, noninvasive, elasticwavegenerators/receptors that canbe easily affixed to a structure. Piezoelectric wafer active sensor installation on the health-monitored structure is an important step thatmay have significant bearing on the success of the healthmonitoring process. The purpose of this paper is to explore the durability and survivability issues associated with various environmental conditions on piezoelectric wafer active sensors for structural health monitoring. The durability and survivability of the piezoelectricwafer active sensor transducersundervarious exposures (cryogenic andhigh temperature, temperature cycling, outdoor environment, operational fluids, large strains, fatigue load cycling) were considered over a long period of time. Both free piezoelectric wafer active sensors and bonded piezoelectric wafer active sensors onmetallic structural substrates were used. Different adhesives and protective coatings were compared to find the candidate for piezoelectric wafer active sensor application in structural healthmonitoring. Inmost cases, piezoelectric wafer active sensors survived the tests successfully. The caseswhenpiezoelectricwafer active sensors did not survive the testswere closely examined and possible causes of failure were discussed. The test results indicate that lead zirconate titanate piezoelectricwafer active sensors canbe successfully used in a cryogenic environment; however, it does not seem tobe agood candidate forhigh temperature.Repeateddifferential thermal expansionand extended environmental attacks can lead to piezoelectricwafer active sensor failure. This emphasizes the importance of achieving the proper design of