Experimental Study On Borehole Response Of CFRP Laminates Based On FBG Sensors

Composite materials are generally composed of two or more than two kinds of substances,the performance are better than any of a single material. Composite material is composed of matrix and reinforced phase, the matrix can be divided into polymer based, metal based,ceramics based, etc.Composite materials can also be divided into fiber reinforced, particle reinforced etc.. Fiber reinforced resin matrix composite is one of the most widely used and the most common one. Fiber reinforced composite materials has the advantages such as high specific strength and modulus, which make composite materials increasingly widespread. On the other hand, composite material has the feature of high hardness and strength, poor thermal conductivity and anisotropy characteristics, which is closely related with the process layer,tearing, burr drawing, collapse block defect produced with process. Composite material is very sensitive to the hidden defects, and gradually evolved into a fatal flaw in the service process, especially the stratification, which leads to the serious decline in the strength of the structure. The axial drilling force is recognized as the main influence factor of the delamination defects, but it cannot be explained by the mechanism of the defects in all working conditions. The response of composite laminates strain under drilling is studied in this thesis. With the help of pasted on the surface of the sensor and in carbon fiber enhanced composite(carbon fiber reinforced plastics, CFRP) plate embedded fiber Bragg grating(fiber Bragg grating, FBG), strain distribution and response rules are deeply studied, and the main contents are as follows:(1) Drilling defects and damage detection of composite materials is analyzed, and the main application of FBG in the health monitoring of composite structures is researched.(2) Based on FBG sensing principle of FBG, forming process of FBG and carbon fiber pre dip material is analyzed. By using hot pressing machine to real-time monitoring the curing process of double carbon fiber pre-dip to anticipate the curing process of encapsulated FBG sensor, FBG smart CFRP sheet of parallel to the direction of fiber id made. Combined withthe experimental error analysis, strain sensing properties of the encapsulated FBG sensor is researched, and the measurement is calibrated, both to further improve the production process.(3) Establish Matlab 3D data model corresponding to finite element. Research the strain response data extraction of finite element simulation and the Matlab data model interface, and reproduce the results of numerical simulation.(4) Build strain response monitoring system based on FBG borehole, and have a real-time monitoring to the CFRP laminates of borehole strain response. Import the data into the Matlab model that is established and analysis the result. Compared strain response of two conditions, make an evaluation to the monitoring effect of the bore sensors which buried FBG in CFRP interior.