<title>Design, fabrication, and evaluation of an optical fiber sensor for tensile and compressive strain measurements via the use of white light interferometry</title>

Abstract

An embedded, intensity-based fiber optic sensor was previously designed and evaluated for strain monitoring in advanced fiber reinforced composites under dynamic loading conditions. The original sensor design involved the use of two multimode fibers, each with a cleaved end. These fibers were fitted into a glass capillary and were secured in position via a fusion splice at each end of the capillary. However, the effective operational strain range of this sensor design was limited primarily to tensile loading. In order to use this sensor under compressive loading regimes, it was necessary to develop a technique to construct the sensor with a known separation of the fiber end-faces. In effect, the sensor is an extrinsic Fabry-Perot interferometric sensor. The signal processing was based on a scanning monochromator. The feasibility of using the optical fiber sensor for tensile and compressive strain measurements was demonstrated. The sensor was also used to obtain in-situ stiffness reduction data during the fatigue testing of a cross-ply carbon fiber reinforced composite. An analysis of the relationship between detection sensitivity and sensor geometry is also presented.