Damage monitoring of CFRP laminates with open holes using chirped FBG sensors

This study proposes a new approach to monitoring damage states of a CFRP cross-ply laminate containing an open hole, by taking advantage of a chirped fiber Bragg grating (FBG) sensor embedded near the hole. A holed specimen with an embedded chirped-FBG sensor was subjected to tensile loadings, and multiple damage, i.e. splits, transverse cracks and delamination, was then observed by soft X-ray radiography. Also, the reflection spectrum was measured at various applied strain levels. The simulation results on the extension of multiple damage states and on changes in the spectrum shape agreed well with the experimental ones. A numerical study verified that the spectrum shape was strongly correlated with the damage pattern. Based on this information, we then performed simple damage-pattern estimation from the spectrum shape. Through this study, we demonstrated the superior potential of the chirped FBG sensor for monitoring damage in composite laminates.