Numerical Investigation of the Optimum Placement Locations of Optical Fiber Bragg Grating Sensors for the Health Monitoring of Bonded Composite Repairs

Abstract

Abstractthe use of optical Fiber Bragg Grating sensors (FBG) embedded into composite laminates has proven to be an efficient way for the monitoring of the strain field inside composite laminates. The current work focuses on the use of such sensors for structural health monitoring of bonded composite repairs, often used in the aerospace as well as in the maritime industry. In such applications, the embedding location of the FBG sensors is of great importance, since apart from general strain measurements of the composite, they provide the ability of detecting whether a crack has propagated in the metal or a debonding has occurred between the metal and the composite. Within the current work, a representative case of bonded composite repair of a cracked metallic structure is examined and a series of 3D elasticity linear static finite element models are developed. Various crack lengths and patch disbond sizes have been studied while varying strain distributions were recorded along numerous paths inside the structure. Having recorded and analyzed these strain distributions, certain guidelines have been derived concerning the optimum FBG placement inside the patch, in order to ensure efficient structural health monitoring.