Reflected spectra prediction for chirped fibre Bragg gratings used for disbond detection in composite/composite bonded joints

Abstract

In this paper it is shown that a chirped fibre Bragg grating sensor embedded within a composite adherend can be used to monitor disbond initiation and propagation in an adhesively bonded single lapjoint. Characteristic changes in the reflected spectra from the sensor indicate both disbond initiation and the current position of the disbond front to within about 2 mm (a distance which depends on adherend material and sensor position in relation to the adhesive bondline). When the sensor extends the full overlap length, disbond initiation from either end of the overlap can be monitored. The results have been modelled using a combination of finite-element analysis and commercial software for predicting FBG spectra; the predicted spectra are in very good agreement with experiment. The CFBG sensor technique could provide the basis for monitoring a wide range of bonded joints and structures where one adherend is a composite material