Research On The Health Monitoring Of Material Structure Using Fiber Grating

According to the unique advantages of light weight, high spatial resolution, easy to form thequasi-distributed network and so on, Fiber Grating has made the structural health monitoringtechnology based on fiber sensing into a new hot spot focused by the current domestic andinternational researchers, with the great application prospect in the field of aviation and civilstructure health monitoring. This dissertation aims to research on the application of fiber gratingin aviation and civil structural health monitoring, including the fracture monitoring for CFRPcomposite structure, the impact of extreme environment on the FBG-based tensile strainmonitoring for CFRP composite structure, the monitoring for reinforcing bar corrosion inconcrete and the monitoring for asphalt pavement. All these work provides theoretical andpractical preparation for promoting the availability of the structural health monitoringtechnology.The main achievements are described as follows:(1) Theoretical analysis of FBG and LPFG is achieved, and the coupled equations of the fibergrating is derived, providing a theoretical basis for the sensing characteristic of the fiber grating.By the spectrum and sensing characteristic simulation of FBG and LPFG, the basis of the gatelength selection and the sensitivity coefficients are given. The sensitivity of LPFG resonancepeak amplitude changing with transverse load and its direction correlation is researched byexperimental analysis.(2) Based on the analysis of acoustic emission and CFRP composite fracture theory, the strainresponse signals of the CFRP composite tensile specimen and the overall CFRP compositestructure induced by the internal fractures and cracks are acquired by FBG sensing monitoringsystem. The internal fracture and the expansion of crack have been got. At the same time, thereliability of FBG sensing system in extreme environments is verified.(3) High speed demodulation system based on the filtering effect of the optical filter is studiedin order to research dynamic signal monitored by FBG sensor. The methods of the FBG vibrationand impact monitoring are proposed for the thin plate. The experimental results show that theresponse effects of the system for vibration and impact monitoring are good and have a highresolution, which can meet the requirements of the signal acquisition.(4) Base on the mechanism of steel corrosion in reinforced concrete and the refractive indexcharacteristic of LPFG, a corrosion monitoring method in stages is proposed and a LPFG rebar corrosion sensor is designed to detect the changes of refractive index around rebar in concretecaused by chloride and liquid rust. Meanwhile, a LPFG rebar corrosion sensor which canmonitor the corrosion status at360°is designed, and the buried experiment is achieved well.(5) Introducing FBG and LPFG into the area of the strain and hydrodynamic pressure inasphalt pavement, a LPFG transverse load effect-based pressure sensor， a FBG straineffect-based pressure sensor and a LPFG bending effect-based hydrodynamic pressure forasphalt pavement are designed respectively. The experiments have been done and the goodresults have been obtained.