Process Monitoring and Damage Detection in Composites Using FBG Sensors

The residual strain will be generated during the prepreg curing process when the composite materials were manufactured, and the residual strain in the composites will markedly influence the quality of the composite materials. In order to realize on-line monitoring the prepreg curing process and on-time detecting the damages in the composites, optical fiber Bragg grating (FBG) sensors were embedded inside the laminated composites when the composite plates were produced. The changes of the Bragg wavelength of the FBG sensors were measured using an optical fiber spectrometer. The strain changes during the prepreg curing process were monitored with the FBG sensors, and then the progress of the composite solidification process was analyzed. The reflection spectra of the FBG sensors were measured, and the internal damages in the composite specimens were monitored according to the spectrum measurement results. Experiment results indicate that the FBG sensing technology is feasible for monitoring prepreg curing process and detecting the interior damages in the composites.