Spatially continuous strain monitoring using distributed fiber optic sensors embedded in carbon fiber composites

A distributed fiber optic strain sensor based on Rayleigh backscattering, embedded in a fiber-reinforced polymer composite, has been demonstrated. The optical frequency domain reflectometry technique is used to analyze the backscattered signal. The shift in the Rayleigh backscattered spectrum is observed to be linearly related to the change in strain of the composite material. The sensor (standard single-mode fiber) is embedded between the layers of the composite laminate. A series of tensile loads is applied to the laminate using an Instron testing machine, and the corresponding strain distribution of the laminate is measured. The results show a linear response indicating a seamless integration of the optical fiber in the composite material and a good correlation with the electrical-resistance strain gauge results. The sensor is also used to evaluate the strain response of a composite-laminate-based cantilever beam. Distributed strain measurements in a composite laminate are successfully obtained using an embedded fiber optic sensor.