N. Tralshawala, E. J. Nieters, M. Radebach, S. C. Nath, GE Global Research Center, Niskayuna, NY

Summary:

Various structural health monitoring (SHM) applications require sensing the status of hard to access components using visual, eddy current (EC) and ultrasound (UT) inspections. This requires significant disassembly for access and reassembly after inspection. These inspections are costly from labor and downtime perspectives and must be limited to specific intervals. In addition, there is a possibility of catastrophic failure between scheduled inspection intervals. This paper describes the development of bonded EC sensors and interface electronics to address this issue. The design allows for the use of existing instrumentation and thus requires no significant infrastructural or training costs to deploy these sensors. The sensors/arrays would be bonded to structures being monitored during one of the scheduled inspection/maintenance periods when the structure is disassembled. After reassembly, the sensor can be interrogated at regular intervals or, depending on the application, could even be continuously in operation.

The EC sensor consists of a multilayer structure that comprises metal layers and dielectric layers. The EC sensor(s) is/are then bonded to the structure(s) being monitored. The technology developed is easily scalable to large scale manufacturing of flexible EC sensors/arrays. Choice and integration of various materials and processes are optimized to create a product that meets reliability standards for critical applications in harsh environments for real-time structural health monitoring. Testing procedures are based on specification limits from various military and commercial standards for sensors and electronics as well as existing SHM applications. The sensors have survived some preliminary thermal cycling, humidity and stress fatigue cycling studies and these data shall be presented. Future tests will incorporate pressure cycling and exposure to chemicals, sand, mold etc., and extensive Design of Experiment (DOE) techniques will be used for technology selection.

The main focus has been airframe SHM. Discussions with Airbus, Boeing, United/Northwest airlines, and the military are on-going to determine suitable applications for these sensors and to flight qualify them. In the future civil structure applications are also envisioned.