## 3 Results and Discussion
Figure 8b further shows the damage zone, presented in red and black, and was used to assess delamination damage. The white damage spot on the lower composite panel shown in Figure 8a, which corresponds to the black spot shown in Figure 8b, might have been produced by the broken carbon fibers and carbonized resin matrix. Damage location data in Figure 8c show that the specimen surface was tilted slightly and that the deterioration depth was about 1.8 mm apart from the top lamina. The yellow zone in Figure 8c, when  
Figure 6: Surface damage pattern and size of four different types of composite-reinforced panels: (**a**) composite-reinforced panel without protection; (**b**) composite-reinforced panel with a full-sprayed aluminum coating; (**c**) composite-reinforced panel with a local-sprayed aluminum coating; (**d**) composite-reinforced panel with a full copper mesh filling. (Unit mm). comparing it with that in Figure 8b, shows that delamination damage may have appeared. The green might correspond to the red carbonized damage zone shown in Figure 8b. The lightning electrical current was a priority to conduct along the aluminum layer direction. Attachment damage mainly appears in the cross-shaped sprayed aluminum zone in Figure 9a, distributed along the 45 degree fiber direction on the top central lamina, which is presented in white and red, and the area around this zone is presented in yellow. Comparison with visible detection shows that the aluminum layer in the damage zone was also melted and vaporized, carbon fibers were broken up, and the epoxy resin matrix had carbonized decomposition in part on the sprayed aluminum coating and in part on the aluminum zone without spraying. It can be seen in Figure 9b that there is an irregular red zone along the 45 degree direction on the top central lamina, where the fiber fracture belt does not run throughout the whole specimen, which implies that not only does the surface specimen appear to have a fiber fracture but the internal specimen also has carbonized deterioration. Delocamination damage was assessed by the obvious change in color in Figure 9b. Damage location data in Figure 9c show that the deterioration depth was about 1.8 mm apart from the top lamina. Figure 8: Echo amplitude, echo location, and location data for composite-reinforced panel with a full-sprayed aluminum coating: (**a**) echo amplitude; (**b**) echo location; (**c**) location data (Unit: mm). Figure 7: Echo amplitude, echo location, and location data for composite-reinforced panel without protection: (**a**) echo amplitude; (**b**) echo location; (**c**) location data (Unit: mm). Both elliptical lightning attachment damage zones mainly appear in the center and top right corners in Figure 10a, which are connected and presented in white and red, and the area around these zones is presented in yellow. It was easy to induce and accumulate an electrical charge on the specimen surface with the coarse copper mesh, and this charge resulted in point discharge. Comparison with visible detection shows that the copper mesh in the damage zone was broken up, melted, and vaporized. A large number of carbon fibers were fractured, and the epoxy resin matrix had carbonized decomposition. Part of the damage zone was distributed with multiple irregular spots. The yellow zone might have been produced by the oxidized copper mesh, which was peeled off of the surface specimen. More of the damage zone of the broken carbon fibers and carbonized resin matrix is shown in Figure 10b, presented in red and black, was used to assess delamination damage. The red spots shown in Figure 10b correspond to the orange spots shown in Figure 10a and can be seen on the lower surface composite panel, where the copper mesh was not oxidized or peeled off. The center point of different irregular concentric circles, inherent flaws and lightning damage, is presented in a different color.