Impact Monitoring Of Laminated Structure Based On Fiber Bragg Grating Sensor Network

With the rapid development of aerospace industry, aerospace vehicle needs to have more excellent adaptive ability to operate safely in the growing complexity of current space environment, so the requirements of aircraft on its material and structure function is getting higher. Traditional metal materials have been unable to meet the needs of aircraft fully, and composite materials,which have high strength ratio, good fatigue resistance, corrosion resistance, insulation, low heat conductivity and other advantages, get a good development and application and have been widely used in the aviation manufacturing industry. However, composite materials can easily generate hidden damage caused by external vibration impact in the using process, such as the drop of the strength ratio and internal crack. To some extent,these invisible damage reduces the reliability of composite materials. Therefore, research on impact of composite materials is very necessary. Fiber Bragg grating sensor is very sensitive to the change of temperature and strain, and has some unique advantages: the thin core diameter, light weight, good flexibility, and suitability for integration with the flexible inflatable structure, and corrosion resistance, strong anti-electromagnetic interference ability,which is widely used. In this paper, based on optical fiber grating sensing technology, the impact monitoring of laminated structure is studied. the main tasks include the following aspects:Firstly, according to the sensing characteristics of fiber Bragg grating sensor and the structural properties of the composite materials, the temperature sensitive characteristic of fiber Bragg grating sensor under loading, the compatibility of composite materials and optical fiber grating sensor and shock sensitive characteristic of different structure state are studied respectively. The independence about the sensitivity between temperature and strain and fiber bragg grating sensor center wavelength shift, the sensitivity of fiber Bragg grating sensor which has different angle on composite layers and stiffened plate structure’s influence on the signals of impact response are explored.Secondly, aiming at the impact and vibration problems of laminated structure, the fiber grating impact location method based on AR model and H distance is proposed. Impact vibration state of laminated structures is analysed. The optimization layout network based on fiber grating sensor is constructed. The monitoring of impact regional is realized and combined with the positioning algorithm based on AR model and the H distance to achieve the identification of impact position.Finally, a kind of fiber Bragg grating impact localization method based on similarity comparison of modal decomposition is put forward. Impact localization system of the fiber Bragg grating is constructed monitoring impact state of plate surface, and then the characteristics which the impactsignal reflects are analyzed; the impact signal gets its mode decomposition, and constructs its IMF signal decomposition vector; this method can be used to obtain IMF decomposition signals of all kinds of impact signals;location coordinates of the test point can be confirmed by means of the similarity comparison between test signal vector and sample signals vector.