Fabrication and Performance of Optical Fiber Grating Sensors Packaged in Composite Substrate

Abstract

Based on the sensing principle of optical fiber grating, a kind of fiber Bragg grating (FBG) sensor packaged in glass fiber/epoxy composite substrate was designed and fabricated. The glass fiber/epoxy composite laminate was used as the bottom substrate, and the glass fiber fabric was used as the covering layer. Then the FBG was encapsulated between the bottom substrate and the covering layer by means of a vacuum-assisted infusion process of liquid epoxy. The only once but fully curing and the pre-curing processes were separately adopted in the process of preparing the glass fiber/epoxy composite substrate. Through the comparison of the two kinds of experimental results, it can be concluded that when the only once but fully curing process is adopted to prepare the glass fiber/epoxy composite substrate, the linearity and repeatability of the temperature response of the packaged FBG sensor are poor, and its relative repeatability error is as high as 10.90%, while the linearity is only 0.99871; when the pre-curing process is adopted before packaging and the secondary curing process is adopted after packaging, the relative repeatability error of the temperature response of the packaged FBG sensor is only 1.87%, and the linearity is 0.99998; besides, its strain sensitivity coefficient is 0.05514nm/kg, and its temperature sensitivity coefficient is 0.02357nm/℃, which is 2.4 times of the temperature sensitivity coefficient of bare FBG sensor.

Keywords

• composites
• fiber Bragg grating
• vacuum-assisted infusion
• pre-curing
• secondary curing