A Continuous Sensor to Measure Acoustic Waves in Plates

An active fiber composite tape with segmented electrodes was modeled for use as a continuous sensor for structural health monitoring of plate structures. The material has unidirectional piezoceramic fibers with interdigital electrodes on the top and bottom surfaces and is poled in the fiber direction. The elastic response of a plate with the modeled sensor was computed in closed form at small time steps, and the coupled piezoceramic constitutive equations were solved. Wave propagation responses and the corresponding sensor voltages were computed in the simulations. The simulations indicate that the continuous sensor can detect damage to the plate based upon high frequency wave propagation characteristics. A continuous sensor comprised of monolithic piezoceramic patches was built and tested to measure simulated acoustic emissions on panel structures. The monolithic patches were used to simplify fabrication of the sensor. The sensor detected simulated acoustic emissions in a fiberglass panel using only one channel of data acquisition. The continuous sensor can potentially reduce the cost, complexity, number of channels of data acquisition, and the weight of monitoring instrumentation to a level where it becomes practical to perform health monitoring on large structures.