Research On Material Damage Detection Based On Fiber Bragg Grating And Acoustic Technology

With the rapid development of modern science and industry, a variety of materials have been widely used in various industries, the structure and quality of material become more and more attention, so it have great significance for the real-time health monitoring of composite structure.In this paper, the acoustic wave technique and optical fiber grating sensing technology are combined, in order to conduct a feasibility study on the damage detection of composite material plate.We choose composite plate as the research object, established the ultrasonic material damage detection system and optical fiber grating demodulation system. This paper will study the composite plate under ultrasonic excitation with the combination of theory and experiments,detecting and receiving damage with fiber grating. First of all describes the significance of research on damage detection material,then do a research on the current photoacoustic combined detection material damage technology research status at home and abroad.Secondly, the theoretical knowledge of ultrasonic wave is briefly analyzed, explain the propagation characteristics of ultrasonic signal in the material plate, the ultrasonic incidence mode in the experiment is discussed. Then, study on the structure and theory of the fiber Bragg grating sensor, fiber Bragg grating strain on the ultrasonic wave causes are investigated, and the ultrasonic reflection of ultrasonic axial effect on fiber grating spectral shift to experimental analysis; and then the corresponding variable wave propagation characteristics in fiber Bragg grating is analyzed in theory, research and analysis fiber Bragg grating paste process, the length of fiber Bragg grating and fiber Bragg grating layout of how to select and optimize the ultrasonic signal can make the response of fiber Bragg grating maximum. Then, the composite damage experiments are carried out to study the use of ultrasonic excitation-FBG receiving method of FBG wavelength demodulation and system, this article expounds in detail the several common fiber grating demodulation method,expounds the advantages and disadvantages of each demodulation methods, the grating matching demodulation method and laser matching demodulation method has done the experimental study, the two systems use in ultrasonic signal testing, the signal acquisition to contrastive analysis, compared sensitivity and demodulation speed of two kinds of ultrasonic demodulation system, verified the feasibility of combining light and sound method for material damage detection. Finally, build the ultrasonic excitation fiber grating test system,using ultrasonic signal as the ultrasonic excitation, water as the transmission medium, ultrasonic signal is propagated to the composite plate, respectively, with a lossless composite plate and a no damage composite plate study on composite plates damage, the experimental results show that, you can determine the initial defects in a composite material plate.