| Compared with metallic materials, advanced composite materials are more anti-fatigue, have lighter weight, better strength-weight ratio, corrosion resistance and long life, and can be used to create complex shapes. It is an inevitable trend to use advanced composite materials to create structures and major projects equipment (such as aerospace structures).Research and engineering applications at domestic and foreign show that composite materials are prone to be damaged because of the tension and compression, impact and fatigue loading on the service work time. It will lead to huge economic losses, casualties, and even disastrous consequences if these injury and damage are not promptly discovered, and then corresponding measures aren't taken. Therefore, the research and development of sensors which meet the requirements of composite materials engineering is the core work to achieve safety monitoring of composite materials and structures.On the basis of summing up extensive literature at home and abroad, the paper has a research on design theory and application technology of composite materials FBG sensor from basic theory, basic experiment and application on the project. And the design theory, the technology of preparation and the application and engineering technology of FBG sensors which were used to monitor composite structures have also been investigated from aspects such as materials, components, structures and so on. The objective is to develop a fiber grating strain sensor which is encapsulated by composite materials, build the safety monitoring system constituted by them, and to achieve the application in the major construction projects. The main work of this dissertation is as following:First, the transmission theory and basic characteristics of FBG sensing were proved and the FBG sensing mechanism of composite materials were analyzed from the requirements of FBG sensing. Since the requirements of the composite materials monitoring, the strength theory, design theory and the related composite molding process were researched. And then the basic design line of FBG composite sensor was summed up.Second, a series of design, production, performance test of composite materials sensor were done based on the strength and stress-transfer theories of composite materials, in accordance with the basic design line of the composite materials sensor, from the composite materials/Sensors/structure compatibility, through the theoretical research and analysis of the fiber grating/sensors/transmission of strain of measured interface. And then through optimization and analysis, the design theory for FBG composite materials sensor was put out base on the strain transmission efficiency.Third, the strain interface transfer mechanism and error correction of the fiber composite material sensor were researched. The strain multi- interface transmission and error correction formula of Fiber Sensor were derived. And then the strain sensing error analyzed and amended using the theoretical and experimental results on self-developed fiber Bragg Grating sensor packaged by composite materials.Fourth, mechanical and sensor performance were tested of the Fiber Bragg Grating sensors packaged by carbon composite materials from the requirement of the compatibility of composite materials/sensors/structure. Mechanical test results showed that, there was no significant impact on the mechanical properties of the composite materials and structures which were embedded in sensors. And the sensors have good adaptability, stability and reliability performance. Sensing performance test results showed that the sensor has good linearity and repeatability, with the value of engineering applications.Fifth, carbon fiber composite materials FBG sensors were used on a reinforcement project of the Yangtze River Bridge. The results showed that the sensor can adapt to the complex stress measurements of composite structures in a variety of objects. And basically realize engineering and practical of the sensor, and has good prospects. |
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