An investigation of the response of embedded near infrared fibre bragg grating (FBG) sensors (830nm) in glass fibre composites under fatigue loading

Conventional FBG sensors operating in near infrared region (Bragg wavelength 830nm) were embedded in samples of 00/900 woven cloth/Vinylester laminates in order to investigate the variation of embedded FBG sensor spectra due to the damage accumulation in the laminate under fatigue loading conditions. It has been seen that the output FBG spectra of the embedded FBG sensors in fatigue loaded samples were distorted and bragg wavelength was broadened. These distortions of FBG spectra are an indication of an asymmetric and non-uniform strain distribution along the grating length of the FBG sensors due to accumulation of damage during fatigue loading. This information is useful for formulating a fundamental relationship between FBG spectral changes and the damage accumulation of composite structures. Further, it has been seen that the sensitivity and durability of the embedded FBG sensors fabricated by conventional writing techniques were excellent for health monitoring of composite structures