2021 Volume 47 Issue 3 Pages 116-125
The use of smart sensors in in-situ monitoring methods for fiber-reinforced plastics (FRPs) has recently attracted significant attention and extensive research is underway. Herein, we focused on a monitoring method that uses a Fresnel-type optical fiber sensor. To realize this, we investigated the measurement accuracy of the Fresnel-type optical fiber sensor to determine the influence of the optical loss on the local bending of the fiber. First, a local bending experiment was conducted on standard and highly flexible optical fibers to characterize their optical losses. Next, the curing degree measurement was performed on locally bent optical fibers, and it was revealed that the amount of optical loss did not affect the accuracy of the degree-of-cure (DOC). Finally, the curing degree measurement of glass fiber-reinforced plastic (GFRP) plates that were molded into a curved shape using vacuum-assisted resin transfer molding (VaRTM), revealed that the optical loss remained unstable for a specific duration. This indicated that it has a significant influence on the accuracy of the DOC. However, fluctuations in the optical loss did not affect the measurement accuracy when the amount of loss was small.
