Global damage index of aerospace-grade CFRP subcomponents with FBG-based sensors

Current composite structures used in aircraft can suffer from barely visible impact damage (BVID) that can compromise the load-bearing function of these structures. Especially damage-prone regions, such as the feet of a skin-stiffener structure, must therefore be frequently inspected for such damage. This increases aircraft downtimes and associated costs. A permanently installed structural health monitoring (SHM) network based on optical fiber sensors is an ideal candidate for performing condition-based maintenance (CBM) on such a structure. Individual FBG sensors have a known potential to detect the presence of BVIDs. In this work we propose a Global Damage Index (GDI) for quantifying the health of a composite component in manner of seconds, based on a network of 60 FBG sensors. We first establish a damage detection threshold and then carry out temperature compensated BVID detection with the GDI.