Research On Electromagnetic Eddy Current Non-destructive Testing Technology For Fatigue Defects Of Carbon Fiber Composite Materials (CFRP)

Carbon fiber reinforced ploymer composites(Carbon Fiber Reinforced Ploymer,CFRP)have been widely used in many industrial fields,and research on non-destructive testing methods for this new type of material has also received increasing attention.The use of non-destructive testing technology to discover various defects in its manufacturing and use processes has a very important role in ensuring safety in production and life and promoting the development of carbon fiber composite materials.Eddy current detection is a non-contact,low-cost,radiation-free,couplant-free detection technology.It is based on the principle of electromagnetic induction between a current-carrying coil and a conductive material.According to the testing requirements of fiber composite materials,this thesis has conducted in-depth research on its electric eddy current detection technology for more common plain weave CFRP in actual use.Based on the in-depth study of the electrical characteristics and eddy current path of unidirectional CFRP,this thesis first proposes a discrete conductivity model of plainweave CFRP,using a double-circular-rotatable coil sensor,and using the sensor impedance signal as the detection signal characteristic quantity pair.The plain-weave CFRP was analyzed by finite element simulation.On this basis,a CFRP detection system for plain weave is designed,and the defects and fatigue of plain-weave CFRP are analyzed and summarized.The research shows that the maximum change in the coil impedance occurs at the maximum value of the conductivity vector of the warp and weft yarns,and the error between the simulation result and the experimental result is less than 0.6%.Therefore,the model proposed in this paper can effectively simulate the electromagnetic characteristics of plain weave CFRP.At the same time,the use of DCR coil sensors can effectively detect the defects and fatigue of plain weave CFRP,and has better visualization.The conductivity of plain weave CFRP changes under cyclic loading.In addition,the fatigue phenomenon of plain weave CFRP can be simulated by changing the conductivity in the discretized model.