Abstract
It has been proven that fiber-optic refractive-index sensors can be used for monitoring cure process of thermosetting resin. In the present paper, process monitoring of GFRP was conducted by embedded refractive-index sensors. The sensors were embedded in 0° and 90° directions of unidirectional GFRP laminates and in resin of prepregs in order to investigate effect of reinforcing fibers on refractive index of resin. The laminates were manufactured at 140℃ and pressure of 0.5 MPa by a hot-press molding device. The experimental results showed that the effect of reinforcing fibers had remained small until cure process finished, however thermal residual stress caused by reinforcements affected refractive index of prepreg at cooling. Therefore, it was found that cure index of FRP prepregs could be measured by refractive-index sensors. In addition, it appeared that the refractive-index sensors were available to monitor air voids in resin qualitatively during molding.
