Damage detection in holed composite laminates using an embedded FBG sensor

This paper discusses damage detection in a holed CFRP laminate under static and cyclic loading using an embedded fiber Bragg grating (FBG) sensor. In order to detect the damage extension in the laminate, the change in the spectrum shape was measured using an embedded FBG sensor and was compared with that obtained by numerical simulation. The shape of the reflection spectrum did not change during the cyclic load test; however, it did change with increased strain in the static load test, due to damage around the hole. To clarify this difference, the polished surface of the cross section of the specimen was analyzed. Debonding was observed between the optical fiber and matrix during the cyclic load test. These results lead us to conclude that fatigue damage around a hole in a composite laminate may not be detected with an FBG sensor due to the debondings.