Applicability of an Optimized Fiber Optic Smart Structure

In recent years, fiber optic smart structure is widely studied because of its intrinsic benefits [1] [2]. One of the most striking evolvements is the technology, of which FBG (Fiber Bragg Grating) sensor systems are embedded in fiber reinforced composite materials, so that any ambience induced responses of the host structures can be monitored in real time, consequently proper actuations are initiated. Thus a neural system is realized. This work reports an entire optimization process of the FBG sensors embedded in Graphite/Epoxy composite material. Moreover, performance of the sensor system was observed and the applicability is discussed. Due to the mechanically orthotropic characteristics of the Graphite/Epoxy composite material, two FBG sensors were orthogonally embedded along the two principle axes in mid-plane of the specimen. When strain load was applied along one of the axes, longitudinal and shear responses of the structure were simultaneously monitored, hence its orthotropic properties were determined. Further, any randomly oriented strain applied to the specimen will be analytically quantified along the two sensors. Recurring to surface mounted resistance strain gage concept, the embedded FBG strain gage array was recalibrated, and its sensing alterability is quantified. This work tends to provide a quantitative discussion on FBG sensors’ residual erroneousness after an optimized embedment, the conclusion may give designers a reference to properly interpret FBG sensors’ performances, in case they are used as an embedded strain gage.