## 4 Simulation Analysis of the Designed Probes  
### Analysis of Probe Scanning Modes  
In the process of manufacturing CFRP, different fiber orientations can be defined manually according to specific requirements. The electrical conductivity varies in different directions, resulting in different eddy current distributions. Taking the CFRP sample with an orthogonal ply layup as shown in Figure 5 as an example, analyze the eddy current distribution in the multi-directional laminate through simulation. Figure 8 shows the eddy current distribution in different layers of the CFRP sample as depicted in Figure 5 when the center of the designed probe is located at x = y = 0. Here, (a) and (c) represent the eddy current distribution in the first layer of the sample (fiber direction 0\({}^{\circ}\)) and the third layer (fiber direction 0\({}^{\circ}\)), respectively, while (b) and (d) represent the eddy current distribution in the second layer (fiber direction 90\({}^{\circ}\)) and the fourth layer (fiber direction 90\({}^{\circ}\)), respectively. Figure 8: Eddy current distribution in CFRP sample: (**a**) first layer (0\({}^{\circ}\)); (**b**) second layer (90\({}^{\circ}\)); (**c**) third layer (0\({}^{\circ}\)); (**d**) fourth layer (90\({}^{\circ}\)). \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Probe Parameters**} & \multicolumn{4}{c}{**Excitation CoilParameters**} & \multicolumn{4}{c}{**Detection Coil Parameters**} \\ \cline{2-10}  & \(D_{e}\)/mm & \(H_{e}\)/mm & \(K_{e}\)/mm & \(N_{e}\) & \(S_{e}\)/mm & \(D_{r}\)/mm & \(H_{r}\)/mm & \(K_{r}\)/mm & \(N_{r}\) \\ \cline{2-10}  & 6 & 1 & 1.2 & 120 & 1 & 10 & 1.2 & 1 & 120 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Probe parameters. The arrows in Figure 8 represent the distribution of eddy currents inside the sample, with denser arrows indicating a more concentrated eddy current presence. Based on the distribution of eddy currents shown in the diagram and the magnitude of the eddy current density, it can be observed that in the layers where the fiber direction is 0\({}^{\circ}\), the eddy currents exhibit a tendency to flow along the X-axis. In this case, the fiber direction is the same as the direction of the excitation current, resulting in a larger and more concentrated eddy current induced in the sample. On the other hand, in the layers where the fiber direction is 90\({}^{\circ}\), the eddy currents tend to flow along the Y-axis. Here, the fiber direction is different from the direction of the excitation current, leading to smaller and relatively more dispersed eddy currents induced in the sample. Therefore, eddy currents tend to concentrate in layers where the excitation current direction is the same as the fiber direction. However, the distribution of eddy current directly affects the magnetic field distribution in the CFRP sample and the effectiveness of defect detection [33; 34]. When defects are located in layers where the excitation current direction is the same as the fiber direction, the detection effectiveness is better. Conversely, when defects are located in layers where the excitation current direction is different from the fiber direction, the detection effectiveness may be relatively poorer. For the above-mentioned problem, this paper proposes two probe scanning modes, as shown in Figure 9. When using scanning mode 1 for eddy current testing, the excitation current direction is along the x-axis. In this case, the eddy currents in the sample are concentrated in the layers where the fiber direction is parallel to the x-axis, i.e., the 0\({}^{\circ}\) layer, as shown in Figure 5. When using scanning mode 2, the excitation current direction is along the y-axis.