Open Access Open Access  Restricted Access Subscription or Fee Access

Piezoelectric Zinc Oxide Nanowires for Use in Acoustic Emission Testing



Acoustic emission testing has proven useful for real-time damage detection in a variety of situations, however the need for externally bonded sensors limits the feasible applications. This work investigates an alternative approach to traditional acoustic emission testing by using piezoelectric zinc oxide (ZnO) nanowires fully integrated into fiber-reinforced polymer composites. The ZnO nanowires are conformally grown on the surface of woven aramid fabrics via a hydrothermal growth process after which the fabric with ZnO nanowires is placed between layers of woven carbon fiber using vacuum assisted resin transfer molding forming multilayer composites. While the nanowires serve as embedded sensors in the samples, the carbon fiber layer serve as electrodes across which the voltage of the composite can be measured. The composite samples are subjected to a standard tensile test during which the sample voltage output is measured using wire leads attached to the carbon fiber electrodes. Damage to the composite sample during testing results in elastic waves which are converted to measurable electric field by the piezoelectric nanowires. The recorded sample voltage is used to detect instances of internal damage by evaluating the amplitude and number of acoustic emission hits during mechanical testing up to the point of failure. The measured voltage is used to detect internal damage to the composite at less than 50% of the maximum strain thus demonstrating the use of ZnO nanowires in real-time damage detection.


Full Text: