<title>Integrated wireless piezoelectric sensors</title>

Abstract

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 temperatufe 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.

A Summary Review of Wireless Sensors and Sensor Networks for Structural Health Monitoring

“…Furthermore, the reflected Lamb wave signals from the MEMS-IDT sensors indicate that the signal response changes in concert with the detected crack size. Ihler et al (2000) have proposed a unique approach to wirelessly monitoring corrosion cracking in aircraft skins. Their wireless system is similar in operation to the RFIDbased wireless sensor proposed by Novak et al (2003) for monitoring corrosion of steel in reinforced concrete.…”

“…Their wireless system is similar in operation to the RFIDbased wireless sensor proposed by Novak et al (2003) for monitoring corrosion of steel in reinforced concrete. The device proposed by Ihler et al (2000) is a wireless crack-wire sensor sufficiently resilient to withstand the extreme temperature cycles encountered during fabrication of carbon fiber composite laminates. The design of the wireless sensor begins with four conductive wires mounted to the surface of an epoxy-based substrate, which in turn is mounted to the surface of an aircraft.…”

Design and selection of wireless structural monitoring systems for civil infrastructures

“…More fl exible wireless sensor modules, such as the 'mote' family, enable the designer to choose the desired transducer, design the power management circuitry, modify the embedded fi rmware, and fabricate an assembly enclosure for the specifi c application. If the greatest amount of fl exibility is required, yet the designer wishes to not design a unit from the ground up, academic prototypes may be purchased that bring additional features such as advanced sensing (e.g., piezoelectrics 41,42 ), feedback control, 43 and the greatest amount of extensibility. In 2006, Lynch and Loh 18 provided a review of available wireless sensors for structural monitoring at the time, but since technology advances so quickly, newer and more advanced wireless sensor models now exist.…”

Wireless Monitoring of Cable Tension of Cable-Stayed Bridges Using PVDF Piezoelectric Films

“…Pereira et al (2000) discussed the possibility of using the embedded wireless telemetry to realize the communications between MEMS sensors and processing microelectronics in munitions. Ihler et al (2000) have studied the feasibility of using integrated wireless piezoelectric sensors for monitoring the integrity of composite structures. However, the work presented in the last two papers is preliminary and further steps are needed to fully realize their proposed systems.…”