Structural Health Monitoring Using Macro-Fiber Composites and Impedance Methods

A current technique that has been the subject of a great deal of study in the structural health monitoring community is the impedance method, which uses high frequency responses to monitor a local area of a structure for changes in structural impedance that indicate damage. To date, piezoceramic sensors, whose electrical impedance is directly coupled with the structure’s mechanical impedance, have been used as both sensors and actuators for impedance measurements and this practice is fairly well developed. However because these sensors are ceramic, they are brittle, making them vulnerable to accidental breakage. They also conform poorly to curved surfaces. In this study macro-fiber composite (MFC) patches, which are flexible in nature, are examined for feasibility of use with the impedance method. Two test structures with both MFC patches and PZTs are considered. Both traditional linear features and newer nonlinear features are used for structural health monitoring. High frequency responses of the MFC patches are examined and they yield damage identification results that are comparable to piezoelectric impedance signals and indicate that MFCs are suitable for impedance sensing and other high-frequency structural health monitoring.