Integrated wireless piezoelectric sensors

Piezoelectric sensor arrays and sensor networks have been suggested as a mean to monitor the integrity of composite structures throughout the service life for instance of an aircraft. Complex sensor systems will require significant additional expenditures with respect to cabling and electronics, with the added weight and effort possibly outweighing any benefits. Sensor positions in remote locations of an aircraft will often necessitate accessibility to these locations for maintenance purposes. For these reasons wireless, integrated sensors have recently become an object of increasing interest. Within the framework of a feasibility study various aspects of integrated wireless sensor systems were investigated in detail. Particular emphasis was thereby laid on issues that are essential from a practical point of view, but that have not been discussed in the literature extensively. As a starting point a trade-off study between different sensor network configurations was conducted, from passive, remotely queried sensors without power supply to fully functional active sensor pads with integrated power supply and electronics. Various concepts for the on-board energy supply of remotely queried sensor pads were studied and a comparison between rechargeable, and single-use batteries was performed. The suitability of different electronic components for integration into carbon fiber composites (CFC) was investigated with particular emphasis on their survivability under typical temperature cycles experienced in autoclave runs. Finally a crackwire sensor as an example of a passive remotely queried sensor system was pursued further in order to show the feasibility of such a wireless system for composite health monitoring purposes.