Analysis Of Energy Density Spectrum Of Low-velocity Impact In Honeycomb Sandwich Panel With FBG

Carbon fiber composite honeycomb sandwich panel is a kind of structure which is applied to the satellite and other spacecraft. It can improve the strength and rigidity of the whole structure, but prone to damage in the use of the process, especially low velocity impact damage. In this paper, a carbon fiber composite honeycomb sandwich panel is selected and the impact test was carried out. The energy density spectrum of impact process is analyzed by using wavelet packet decomposition and empirical mode decomposition. Based on the research, a new type of impact monitoring system based on distributed Fiber Bragg Grating sensor is built. The main research work and results are as follows:(1) Selection of Fiber Bragg Grating sensors in impact experiment. Fiber Bragg Grating sensor has high sensitivity and wide measurement range, and can be used to monitor the impact process. The layout scheme of the fiber grating sensor is designed, a pendulum is used for Impact load. The experimental results show that the 3 longitudinal 6 horizontal sensor placement methods can better monitor the impact of each point. When the specimen is in normal state and the temperature is constant, the center wavelength of the FBG is constant, and the center wavelength can be shifted by the impact.(2) Wavelet packet decomposition results of Fiber Bragg Grating sensor monitoring signal. Using db N wavelet series, the decomposition scale is 5, and the frequency band can be obtained from the low frequency to high frequency with 32 different frequency bands. Through the analysis, it is found that the different sensor placement methods have certain influence on the results of the monitoring. In the energy of the wavelet packet, the change of the thirteenth order signal is obvious, which can be characterized by the impact process. The energy of the wavelet packet can reflect the response of the specimen in the frequency domain.(3) Empirical mode decomposition results of Fiber Bragg Grating sensor monitoring signal. The original signal is processed by anti-symmetric extension method. K takes 0.2 with the white noise amplitude. M takes 100 with the number of execution. 5 IMF components(IMF1~IMF5), and a residual function RES. are received. Each IMF component has certain significance, including high frequency, low frequency, global trend, maximum amplitude and time scale of the original signal.Research results show that the impact monitoring system using distributed Fiber Bragg Grating sensors can used to monitoring the impact process of honeycomb structure, by means of the wavelet packet decomposition and empirical mode decomposition analysis to monitor the signal can understand the process of the impact of the honeycomb structure.