A study on the correlation between PZT and MFC resonance peaks and damage detection frequency intervals using the impedance method

Impedance-based structural health monitoring uses collocated piezoelectric transducers to locally excite a structure at high frequencies. The response of the structure is measured by the same transducer. Changes in this response indicate damage. Frequency range selection for monitoring with impedance-based structural health monitoring has, in the past, been done by trial and error methods, or been selected after analysis by engineers familiar with the method. For future applications it is desirable to be able to automatically select frequency ranges, perhaps even before installing the system. In this study, analysis of the measurement change through a damage metric is examined and related to characteristics of the measurement. Specifically, an outlier detection framework was used to statistically evaluate the sensing ability of the transducers at various frequency ranges. The variation in undamaged measurements is compared to the amount of change in the measurement upon various levels of damage. Testing was performed with both solid plezoceramic transducers and macro-fiber composite (MFC) piezoelectric devices of different sizes bonded to aluminum and fiber reinforced composite structures. The results indicate that frequency ranges containing a resonance of the actuator are more suited for structural health monitoring.