The application of PZT sensor networks in degradation monitoring of composite aeronautical structures
Krzysztof Dragan, Michał Dziendzikowski, Artur Kurnyta, Andrzej Leski
Quarterly No. 4, 2014 pages 208-213
DOI:
keywords: composites, impact damage detection, structure integrated sensors
abstract One of the ideas to develop structural health monitoring systems is to use piezoelectric transducers generating elastic waves in a monitored structure. In the paper, we present an approach to develop such a system with the use of PZT ceramic (lead zirconium titanate - PZT) sensors embedded into the structure of a composite. Elastic waves actuated in an acoustic medium by a network of PZT transducers can be scattered on the discontinuities of the monitored structure, thus giving a possibility to detect such damages. For composites they can be debondings or delaminations caused by impacts. In that case, PZT transducers can be either bonded to the surface of an element or embedded in the internal structure of a composite. Both methods have their own advantages and drawbacks. Apart from increased sensor durability and lower energy consumption when actuating elastic waves, there are also other, more important reasons for sensor embedding. First, when considering structure repairs with composite patches, it can be hard to use PZT transducers attached to the surface due to their exposure to external conditions. Embedding may also increase the damage detection capabilities of the approach. For multilayered structures like Fiber Metal Laminates (FML), it may allow one to assess the state of each layer separately and to distinguish between inner layers delaminations and debondings between layers made of different materials. In the paper, we present an approach to detecting impact damages of composite structures which are barely visible on the surface (Barely Visible Impact Damage - BVID). The results of impact tests, signal analysis algorithms and the influence of the composite manufacturing process on chosen transducer properties are presented.