Characterization of fiber optic sensors for structural health monitoring

This paper presents experimental results on thermomechanical behavior of Extrinsic Fabry-Perot Interferometric fiber optic strain sensors (EFPI-FOSS). The objective of this study was to determine the accuracy, strength characteristics, and durability properties of both bare (nonembedded) EFPI sensors, and embedded optical fiber sensors in either a neat resin or aerospace grade composite laminate, Experimental results suggest that the embedded EFPI sensors provide reliable strain measurements for values exceeding 10,000 muepsilon under static loading conditions. A major portion of this study focused on evaluating the long term tension-tension fatigue behavior of optical Fiber sensors. Test data suggest the EFPI sensors provide reliable data up to I million cycles at fatigue strain levels below 3,000 muepsilon. For fatigue strain levels above this value, failure of the fiber optic sensor was observed. While the sensor failed it did not influence the strength and fatigue life of the composite coupons. Considering the design strains used in aerospace components, these results provide evidence that the EFPI sensors will survive during the life of typical aerospace structures.