Strain measurement in unidirectional carbon fibre utilising embedded optical strain gauges

This paper explores the application of Fibre Bragg Grating sensors as a distributed optical strain gauge array, embedded within thin carbon fibre reinforced polymer beams. A brief outline of fibre Bragg gratings is given, followed by an outline of the methods used to produce instrumented composite beam samples. Further instrumentation of one specimen was achieved through the use of traditional surface mounted foil strain gauges, allowing a comparison of transducer methods to be undertaken. The beam specimens were subjected to static and dynamic loading and the strain measured from the fibre Bragg grating sensors is presented in this paper. The experimental results demonstrated that fibre Bragg grating sensors offer a robust and low profile distributed sensor network. In addition, the results showed that the strain measurement sensitivity of a fibre Bragg grating sensor far exceeds that of typical surface mounted foil strain gauges. These experiments investigate the accuracy of the FBG strain measurement when the beam specimens are subjected to static and dynamic deflections.