Conductivity Distribution Characteristics And Electromagnetic Detection Method Of Woven Carbon Fiber Composites

Carbon Fiber Reinforced Plastics(CFRP)has excellent characteristics such as high temperature resistance,corrosion resistance,light weight and high strength.It is widely used in aerospace,wind turbine blades,automobiles,and pressure vessel manufacturing.However,CFRP are prone to cracks or fiber breakage due to the difficulty of precise control of process parameters and the influence of factors such as fatigue load and external force during the production and use process,which poses great safety risks.While the electromagnetic eddy current nondestructive testing technology has the advantages of non-contact,non-radiation and low cost.Therefore,the use of electromagnetic detection technology to study the structural characteristics of CFRP and realize their damage monitoring is of great significance for improving production efficiency and ensuring safety in production and life.The research object of this paper is woven structure CFRP,which is divided into2-D and 3-D.First,based on the anisotropy and heterogeneity of carbon fiber composite materials,two models of block model and yarn model are established for 2-D plain weave CFRP.According to the principle of electromagnetic induction,a 12-coil electromagnetic circular array sensor is designed,placed above the model to obtain the impedance value of the sensor coil.Then based on the sensor resistance value when there is no defect,the crack defect is set on the CFRP board for electromagnetic simulation and experiment,the sensor resistance is smaller when there is a defect than when there is no defect.With this change rule,the CFRP crack damage information is obtained by using the characteristics of the sensor resistance change.The 3-D braided structure has better mechanical properties than the 2-D braided structure.After that,the quasi-static three-point bending damage of carbon fiber composites with 3-D plain and twill weave structure is studied.First,the loadconductivity theory model is derived,and the relationship between load and conductivity changes is obtained.Then according to the 3-D plain and twill weave structure,mechanical and electrical simulations and experiments are carried out.Due to the limitation of the width of the test material,the sensor adopts a smaller doublecoil sensor to obtain the relationship between the load and the sensor coil voltage.The results show that the eddy current non-destructive testing technology can well characterize the electrical conductivity distribution characteristics,crack defects and bending resistance of carbon fiber composites with woven structures.