Monitoring mode II fracture behaviour of composite laminates using embedded fiber-optic sensors

Utilization of embedded Fiber Bragg Grating (FBG) sensors for monitoring mode II fracture behaviour of composite laminate beams containing different delaminations along the thickness-wise direction, by virtue of End-Notch Flexure (ENF) tests, is presented. Non-uniform strain distribution due to the stress concentration at the delamination tip was examined by the way of observing the reflection spectrum from the FBG sensor. The stress concentration in ENF specimens, which are subjected to various applied loads, was analyzed in terms of the shift, shape, bandwidth and intensity of the reflection spectrum. Relationships between the load–displacement graphs and the corresponding reflection spectra under ENF tests were established. In addition, the feasibility and reliability of using the embedded FBG sensors for mode II fracture behaviour monitoring in the composite laminates is discussed.