Effect of the recoating and the length on fiber Bragg grating sensors embedded in polymer composites

In the present paper, the influence of the fiber Bragg grating (FBG) length and its coating on embedded FBGs in polymers is evaluated. Different FBG lengths and coatings, uncoated and acrylate-recoated, are used. The evolution of their spectra is also followed during laminate curing on a hot-plate press. The Bragg gratings are used as optical fiber sensors, and their sensitivity and reliability are analyzed. The resulting sensor signal characteristics and the strain answers to different loading modes, i.e. tensile, flexural and through-thickness compression, are also studied.