A relocatable resonant FBG-acoustic emission sensor with strain-insensitive structure

A novel resonant fiber Bragg grating (FBG) based acoustic emission (AE) sensor with relocatable, strain-insensitive and enhanced sensitivity structure is demonstrated for structure health monitoring (SHM) in this paper. With one end of the sensing FBG bonded to a polyimide (PI) plate acoustically coupled with the investigated structure via couplant and the other end free, the sensor can be easily redeployed around the monitored structure surface and get rid of the interference from the strain applied on the monitored structure. Experiment has been conducted to verify the characteristics of this FBG-AE sensor, whose results show that the sensor is insensitive to mechanical strain applied on the monitored structure. It is also shown experimentally that the sensitivity is enhanced by about 1.2 times than the conventional design, while the novel sensor possesses good resonant frequency response to the standard AE waves.