Shape and Load Estimation using Fiber Bragg Grating Sensors for Structural Health Monitoring of Aircraft Structures

Abstract

Aerospace structures are exposed to severe loading and environmental conditions, which necessitates constant inspection and maintenance to improve safety and reliability. Currently, the aerospace industry largely depends on Nondestructive Evaluation (NDE) methods for the detection and characterization of structural damages. These methods are off-line, and hence, the aircraft has to be removed from normal operation and often needs to be disassembled for inspection. As a result, conventional NDE methods have moved towards a new concept, structural health monitoring (SHM), which provides online structural integrity information of the structure and is intended to enhance safety and reliability while decreasing downtime, operating, and maintenance costs. Fiber optic sensor technology, in particular, fiber Bragg grating (FBG) sensors, have become increasingly popular for SHM applications of aerospace engineering due to its unique superior characteristics in terms of small size, electromagnetic immunity, multiplexing capability, high bandwidth, and the possibility to be embedded within the material. Under the scope of the investigations carried out in this thesis, FBG sensors have been explored for the shape estimation and load monitoring applications of aircraft structures. A modal approach for shape estimation is investigated for the purpose of real-time health monitoring, control, and condition assessment of lightweight aerospace structures. The methodology implements the use of FBG sensors to obtain strain measurements from the target structure and to estimate the displacement field. A strain to displacement transformation matrix is derived using mode shapes to estimate the global displacement of a structure from measured discrete strain data. The number of FBG sensors and sensor layout for the shape estimation is optimized using a genetic algorithm. Static and dynamic displacement experiments are conducted on an aluminum plate to verify the algorithm...