Distributed Optical Fiber Strain Sensors Packaged with Polyurethane and GFRP

To apply optical fiber sensors in an extreme environment and fulfill the rapid curing requirement of the thermosetting packaging process on glass fiber reinforced polymers (GFRP) prepreg, a novel fabricating method is proposed in this paper. It packages optical fiber by pouring and brushing the waterborne polyurethane into dry weave GFRP clothes that have bare optical fibers on one side. A special mold with a slot for laying and fixing package materials is designed. The sample with the size of 20 mm × 80 mm × 1 mm is made by adopting the developed mold. The GFRP side of the sample was pasted on the carbon fiber beam with a constant section, and a static loading test was conducted. The strain of the cantilever beam was collected by the packaged distributed optical fiber sensor and demodulated by the OFDR system. According to the Ko theory, the measured strain was converted into the displacement of the cantilever beam. The displacement of the free end of the cantilever beam was compared with the position measured by the machine vision, and the error between the two was small. The experimental results show that the ultra-thin distributed optical fiber strain sensor obtained by rapid packaging can be used for the deformation monitoring of large structures such as wind turbine blades.