Research On Structural Thermal Properties And Strain Field Monitoring Based On Optical Fiber Sensing Technology

Aerospace structures subjected to heat, force, and magnetism, electricity multi-physics couplingin extreme environment, the structural health status are closely related to heat and force load distribu-tion characteristics to large extent. On one hand, aerospace structure can deform when affected bytemperature, and material properties are degraded, result in making the mechanical load capacity di-minished. On the other hand, tube wall of large pressure vessel become thin under pressure and corro-sion, which result in potential risks. Therefore it is necessary to study test diagnostic methods forthermal properties and mechanical properties, which would provide the basis for an accurateassessment of structural security status. Optic fiber Bragg grating (FBG) sensor can sense more than70kinds of physical quantities, like stress, strain, temperature, displacement, etc. It is light weighted,large bandwidth, interference, adaptable and meets the high-precision, long-distance and distributedmonitoring needs. The research works on thermal properties and strain field monitoring methods oftypical aerospace material and structure based on optical fiber sensing technology, the main work in-cludes the following aspects:Firstly, for the needs of thermal expansion and thermal diffusion property monitoring,thermodynamic model of carbon fiber reinforced plastics (CFRP) cylindrical structure is constructed,in order to get thermal strain distribution. A method for monitoring the thermal expansion coefficientis proposed based on fiber Bragg grating sensor and the trends of coefficient of thermal expansionunder thermal cycling conditions is achieved. In addition, a fiber-based water and heat balance me-thod is proposed to test cylindrical CFRP thermal diffusivity and the feasibility and reliability of themethod is verified.Secondly, for the needs of temperature distribution monitoring of metal plate, finite element me-thod is used to analysis metallic structure and composite structures thermodynamic mode. By buildinga distributed FBG sensor network, effective monitoring of critical areas of the metal plate structuretemperature distribution is achieved. With multi-sensor information fusion, A GUI interface is de-signed based on MATLAB data acquisition and processing, and achieve showing temperature con-tours online in real time.Thirdly, for the needs of pressure vessel health monitoring requirements, characteristics of strainfield distribution under different load conditions are analyzed by means of finite element method. Astrain field reconstruction program is proposed based on distributed fiber sensor network. WDM sen-sor network technique and optical frequency domain reflectometry technique are used to study pres- sure vessel strain field respectively. At last, a press vessel strain monitoring software is designedbased on LabVIEW.Finally, according to intelligent morphing wing actuator control objectives, simulation of flexiblewing trailing edge is conducted. Based on control feature of hydraulic servo system, morphing wingPID control software is designed combined with LabVIEW PID Toolkit.