Damage identification in a holed CFRP laminate using a chirped fiber Bragg grating sensor

This study proposes damage identification for holed CFRP cross-ply laminates using an embedded chirped fiber Bragg grating (FBG) sensor. We investigated changes in the reflection spectrum of the chirped FBG sensor due to damage near the hole. The reflection spectrum of the chirped FBG sensor was further studied by estimating the strain distribution along the gage section as an inverse problem based on the spectrum shape. We experimentally confirmed that the reflection spectrum of the chirped FBG sensor changed distinctively within certain wavelengths when each type of damage (transverse cracks or delamination) occurred and extended. Local strain changes were estimated from the reflection spectrum of the chirped FBG sensor; their locations coincided with those for the observed transverse cracks. We also demonstrate damage identification for the holed specimen and conclude that this feature of the chirped FBG sensor provides successful identification of a damage pattern near the hole.