Cure Monitoring of FRP by FBG and Refractive-Index Sensors

Abstract

In the present study, we propose a system for monitoring cure process of FRP prepregs during hot-press molding using dual light sources, FBG sensors and refractive-index measurement. The optical system is composed of a 1310 nm narrow-band FP-LD light, a 1510nm broad-band SLD light, 1300/1500 WDM couplers, a spectrum recorder and an optical power meter. The FBG sensors have a distal end at which Fresnel’s reflection between glass and resin occurs. The reflected 1310nm light form the distal end and the FBG reflection (about 1550nm) were divided into two individual paths by a WDM coupler. The power of 1310nm light was measured by an optical power meter and used for calculating refractive index of matrix resin. Spectra of the FBG light were recorded by a spectrum analyzer. In this study, GFRP prepregs were used for the experiments. From the results in the present paper, it was found that the our monitoring system monitor both cure index and strain during molding quantitatively. In addition, it apperaed that the system can be used for monitoring existence of air voids.