Finite Element Analysis Of Eddy Current Testing Of Carbon Fiber Reinforced Polymers

Because of the superior performance carbon fiber reinforced composites (CFRP) are widely used in manufacturing of aircrafts, automobiles and ships, chemical engineering, electrical equipment and other fields, and are especially highly valued in aviation, ships and nuclear power equipments. However, composite structures have defects during manufacturing and are damaged in using inevitably. Most of defects occur suddenly without omen, which will cause serious consequences. Therefore, nondestructive testing of CFRP is very important.Infrared testing, X-ray testing and ultrasonic testing are the major and effective testing techniques for CFRP at present. Few studies have been done in the eddy current testing (ECT) of CFRP. In this thesis, we study the ECT of CFRP based on the electromagnetic field theory and the finite element (FE) method. A three-dimensional FE model is developed using Fortran language to simulate the ECT of CFRP. By analyzing the simulation results, we can get the eddy current distribution in CFRP, the induced voltage of coil, and the magnetic field signals on structure surface, which contribute to obtaining defect information.FE simulation is of guiding significance to the research of ECT of CFRP. The computed eddy current distribution in CFRP follows the characteristics of electric anisotropy of CFRP. The agreement between the analytical solution of coil impedance variation and the simulation result proves that the FE simulation is reliable. The skin effect in electrically anisotropic materials has also been studied. Simulation results show that eddy current in CFRP decays faster than that in isotropic materials. The thesis also investigates the testing of fiber breakage and delamination. The induced voltage and magnetic field signals are computed. Results show that the ECT technique is good for testing fiber breakage and delamination.