Identification of failure mechanisms in a smart composite actuator with a thin sandwichedPZT plate based on waveform and primary frequency analyses

Abstract

In the present work, the monitoring of an acoustic emission (AE) activity has beenemployed to investigate the failure mechanisms of smart piezoelectric composite actuatorswith a thin sandwiched PZT plate during bending fracture tests. Three kinds of specimensconsisting of woven fabric fiber skin layers and a PZT ceramic core layer are loaded with aroller and the AE activity is monitored in real time during the entire loading by using aresonant type AE transducer mounted on the specimen. Post-failure observationsare conducted to identify particular features in the acoustic emission signal thatcorrespond to specific types of failure events. AE characteristics from monolithic PZTceramic are first examined to distinguish different AE signals from various possiblefailure mechanisms in the smart piezoelectric composite actuators. AE signalsare analyzed in terms of AE event count and AE cumulative energy, and areclassified into four different signal types based on the waveform and the primaryfrequency which is obtained by a short time Fourier transform (STFT). As aresult, the behavior of the four classified different AE signal types according to thewaveform and the primary frequency successfully describes the failure process of thesmart piezoelectric composite actuator with a thin sandwiched PZT plate showingvarious and multiple failure mechanisms. Finally, it is elucidated that each classifiedsignal type is related to the specific failure mechanism within the smart compositeactuator, and the AE characteristics are summarized in table 1, in association withthe individual failure mechanism of the smart piezoelectric composite actuator.