Research On The Impact Monitoring Of Composite Structures With Embedded Fiber Bragg Grating

With the rapid development of the aerospace industry, aircraft service environment has become more and more complex. Some advantages of composite materials are good fatigue resistance ?corrosion resistance ?insulation and low thermal conductivity etc. The proportion of which used in aircraft is larger and larger, honeycomb sandwich structures of composite materials are used widely on aircraft. However, composite materials and honeycomb sandwich structures of composite materials are very sensitive for the impact load, its structure can be injured of matrix cracking, carbon fiber fracture, carbon fiber delamination and honeycomb core collapse and so on when composite materials structure is subjected to impact load, and these injuries seriously impact safety performance and service life of the aircraft, so it's very important to do health monitoring and evaluation for aircraft.FBG(Fiber Grating Sensor) sensors have unique advantages of small size, anti-electromagnetic interference, high sensitivity, being easy to build distributed sensor network and the integration with composite materials etc., which has been widely used in the field of structural health monitoring.Therefore, this paper studies the impact monitoring for composite materials and honeycomb sandwich structures of composite materials, the main work includes the following aspects:First, using the character of FBG sensors easily integrated with composite materials, FBG sensors and honeycomb sandwich structures of composite materials are integrated, and proposing the method of the way of leading fiber gratings port and demonstrating survival proportion of FBG sensors, then doing static loading and impact loading experiments for fiber grating buried in honeycomb sandwich structures of composite materials, studying dynamic and static sensitivity characteristics of embedded FBG sensors.Secondly, using honeycomb sandwich structures of composite materials builds impact monitoring system of embedded FBG sensors network.Analyzing the characteristics and differences between the impact response of the same FBG sensor with different embedded layer and the different FBG sensor with the same embedded layer, then proposing an algorithm of impact position identification based on the maximum vector inner product, initial realizing the impact load position recognition.Finally, aiming at the demand of composite impact load monitoring, a distribute FBG sensors network impact monitoring system is constructed. The impact response signal was decomposed using EMD technique, extract the fractal dimension of the IMF signal of decomposed as the feature ofimpact point, then an algorithm of impact load location based on EMD fractal is proposed, which can realize the location of impact load.