## 4 Conclusions  
In this study, finite element analysis models were developed to assess lightning-induced damage in both original and patch-repaired composite laminates, based on electro-thermal coupling effects. The model's accuracy was validated through comparisons with numerical simulations and experimental results. Due to the misalignment of fibers at the junction between the patch and the laminate, the repaired structure experiences more severe lightning-induced damage when subjected to the same lightning current. Therefore, the application of an aluminum coating to the repaired structure is optimal, although potential challenges such as adhesion durability under service conditions and electrochemical corrosion risks between carbon fibers and aluminum should be considered for practical repair solutions. The following conclusions can be drawn:  
Figure 12: Patch repair assembly diagram for composite laminates with cross-shaped aluminum coating. Figure 13: Lightning ablation damage on patch-repaired laminates with cross-shaped aluminum coating. (**a**) First layer; (**b**) second layer. 1. Patch repairs are unable to evenly distribute the current and heat generated by lightning strikes in contrast to the original structure, leading to current penetration along the thickness direction due to dielectric breakdown in the upper layers. This results in greater internal lightning damage, with the damage area increasing by 33.67% compared to the original structure,
2. Applying an aluminum coating on the repaired laminate's surface reduced the current density through the patch and laminate, resulting in a 78.6% decrease in damage area under a 100 kA peak current. However, this protective strategy would lead to a significant weight increase when scaled up for multiple strike locations,
3. Reducing the width of the aluminum coating minimizes weight. When the width is reduced to 20 mm, the current dispersion efficiency decreases. Further reduction to 10 mm causes the boundary of ablation damage to extend beyond the patch's edge, significantly increasing the ablation area and markedly diminishing the protective effect of the aluminum coating,
4. Applying cross-shaped aluminum coatings to the repaired laminate's surface provides additional conductive paths, facilitating a more uniform dispersion of lightning current and concentrating damage within a relatively smaller area, This results in a significant reduction of 79.24% in the damage area compared to the uncoated controls. Simulation results based on electro-thermal coupling confirm the effectiveness of the cross-shaped aluminum coating in reducing lightning-induced damage to the patch-repaired structure. This finding also paves the way for the development of more effective repair techniques and lightning protection strategies in composite material applications. Future work could benefit from incorporating thermo-electro-mechanical coupling, particularly by considering the thermal expansion coefficient of the aluminum coating. Additionally, improving repair durability and minimizing maintenance frequency represent critical research directions for more sustainable solutions. The application of protective layers such as Tedlar films prior to aluminum coating deserves investigation as a potential approach to enhance long-term performance. These advancements would collectively provide a more comprehensive understanding of how thermal, electrical, and mechanical effects interact in repaired composite structures while extending their service life. Conceptualization, Z.S., Y.S. and K.M. ; methodology, Z.S., Y.Z., Y.S. and H.H. ; software, Z.S. and T.S. ; validation, Y.Z. ; formal analysis, T.S. ; data curation, H.H. ; writing--original draft preparation, Y.Z. ; writing--review and editing, T.S. ; visualization, Y.Z. and T.S. ; supervision, Z.S., Y.S. and K.M. ; project administration, K.M. and Y.S. All authors have read and agreed to the published version of the manuscript.