We have developed a distributed strain measurement system using fiber Bragg grating (FBG) sensors, based on optical frequency domain reflectometry (OFDR) which can measure strain distributions with a high spatial resolution of less than 1 mm at an arbitrary position along a long gauge FBG. In addition, quasi-distributed measurement is also possible by using multiplexed FBG sensor arrays. In this study, we applied this measurement system to the strain monitoring of a composite wing structure made by vacuum assisted resin transfer molding (VaRTM) during a series of load tests, and evaluated its applicability. We could successfully equip inner and outer skins of the wing box with several long gauge FBG sensors and multiplexed FBG sensor arrays. The measured results by multiplexed FBG sensor arrays showed the overall deformation of the wing box. On the other hand, strain distributions of strain concentration zones were successfully measured by long gauge FBG sensors. Consequently, we can say that we confirmed the applicability of our strain measurement system by OFDR to the monitoring of a full-scale composite structure.
