Composite Material Characterization using Eddy Current by 3D FEM Associated with Iterative Technique

Abstract

In this paper, an iterative technique, employing the T formulation associated with the finite element method, based on Maxwell's equations and the Biot-savart law, is used for analyzing the density of eddy currents in composite carbon fiber reinforced polymer (CFRP) materials. For this purpose, a code has been developed for solving an electromagnetic 3D non-destructive evaluation problem. This latter permits the characterization of this CFRP and determinate of fibers orientation using the impedance variation which is implanted in polar diagram. Firstly, the obtained results are compared with those of the analytical model. This comparison reveals a high concordance which proves the validity of the proposed method. Secondly, three different applications are shown for illustrating the characterization of unidirectional, bidirectional and multidirectional piece using a rectangular coil plotted in normalized impedance diagram.

Use of Two Open-Terminated Coaxial Transmission-Lines Technique to Extract the Material Relative Intrinsic Parameters

“…This comparison technique results confirm that the new technique is suitable for extracting the material relative permittivity when using equation (18). Using Equation ( 18)…”

“…These results indicate that using equation ( 18) is better than using (13). Curves coming from the two transmissionline technique (TTLT) and the one using equation (18) are in close proximity, while the sketched curve got by using equation ( 13) is not closely related in this part of the frequency range. Using Equation ( 18)…”

“…Simple to implement, the technique is broadband and covers easily frequency range [1.5-15] GHz. We have shown the importance of using equation (18) which is related to equation ( 9) through its propagation constants that have helped to determine automatically the Hcoefficient. Aside from the purely technical aspect that structure limitations are caused by the antenna behavior, the test fixture radiates when it reaches a certain level of microwave frequencies, resulting in a loss of accuracy.…”

“…The accuracy can reach up to 7%, but it decreases to around 3% when frequencies increase to 4 GHz and higher. If we assume that the SUT is not magnetic (μ r '≈1), applying equation (18) leads to extraction of the material relative permittivity, otherwise, the relative permeability is extracted by supposing the material is not electric (ε r =1). Above all, the use of equation ( 18) requires four linearized phase constants or electric angular θ along with two measurements for each test cell length.…”