Damage detection and monitoring in composites using piezoelectric sensors

The use of piezoelectric transducers for structural health monitoring (SHM) of composites is increasing due to their relatively low cost, small size, durability, and low power consumption. There is a wealth of research supporting their use for passive and active SHM, yet few studies combine the two. In this work, a composite cylinder is subjected to multiple cycles of mechanical loading/unloading in a three point bending configuration. The specimen is instrumented with eight piezoelectric wafer active sensors (PWAS), used as passive receivers of acoustic emission (AE) signals during loading. Active monitoring of the specimen is performed using the same piezoelectric sensors, successively, as transmitters and receivers of guided waves, in a pitch-catch configuration. The axisymmetric L(0,2) mode at 250 kHz is shown to be attractive for long distance propagation between axially aligned sensors.