Developmental Status of SHM Applications for Aircraft Structures Using Distributed Optical Fiber

This paper reports the current developmental status of our structural health monitoring (SHM) technology for aircraft structures. Our SHM technology is based on Brillouin optical correlation domain analysis (BOCDA), which is one of the distributed sensing technologies using optical fiber sensors. The authors have been developing, verifying and validating the BOCDA-SHM system. The airborne BOCDA-SHM device, which can monitor strain and temperature simultaneously, has already been manufactured so far, and sensor installation method adequate to aircrafts was developed. The durability to fatigue loads and environments of the device and sensors were also verified. This paper focuses two developmental tests from among developments previously mentioned. One is flight demonstration test conducted in order to verify the BOCDA-SHM system using the airborne BOCDA device and an attached optical fiber sensor. In the test, strain and temperature monitored by the system were agreed closely with those measured by strain gages and a thermocouple. The other is bearing damage detection test conducted in order to evaluate the probability of damage detection at bolted joint portion of carbon fiber reinforced plastics (CFRP). In the tests, micro-damages occurrences could be detected almost certainly by Brillouin spectrum shape changes even if damaged area did not reach the embedded optical fiber sensor.