Detection of disbond initiation and growth in a bonded joint using a chirped fibre Bragg grating sensor

Capell, Tobias F., Ogin, Stephen L., Crocombe, Andrew D., Reed, Graham T., Thorne, Anthony M., Palaniappan, Jayanthi, Tjin, Swee Chuan and Mohanty, Lipi (2007) Detection of disbond initiation and growth in a bonded joint using a chirped fibre Bragg grating sensor. 16th International Conference on Composite Materials (ICCM-16), , Kyoto, Japan. 08 - 13 Jul 2007. 7 pp .

Abstract

Chirped fibre Bragg grating (CFBG) sensors have been used to monitor the initiation and propagation of disbonds in composite/metal bonded joints. The CFBGs were embedded in the glass fibre reinforced plastic (GFRP) adherend of GFRP/aluminium single lap joints (SLJs), which were bonded at elevated temperature. Cooling a SLJ to room temperature resulted in a residual elastic strain due to the different coefficients of thermal expansion of the adherends. SLJs were fatigue loaded, with the CFBG sensor being interrogated at intervals using a broadband light source and a spectrum analyser when the SLJ was in an unloaded state. It was found that the relaxation of the elastic strain due to disbonding caused perturbations in the reflected spectrum from the CFBG sensors which enabled the position of the disbond front to be determined. The experimental results have been modelled using a combination of finite-element analysis and commercial software for predicting FBG spectra.

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