The widespread use of composite materials has led to an increased focus on restoring the mechanical properties of damaged composite structures to ensure system safety. This study combines compression experiments and finite element simulations to investigate the effectiveness of different patch sizes and repair methods, including single- and double-sided repairs, in restoring the structural strength of composite laminates with barely visible impact damage (BVID). The results demonstrate that low-velocity impact significantly affects the strength of the laminate, reducing it to 68.53% of its original strength, highlighting the necessity of patch repair. For composite specimens repaired using patching, an increase in the patch radius consistently enhances strength recovery, reaching up to 93.96% of the original strength. However, this also leads to an increase in weight, suggesting that the patch radius should be selected based on the specific requirements of the application. Furthermore, double-sided patching is preferable to single-sided patching. This approach improves the repair efficiency by 4.96%, primarily due to its ability to provide a more uniform stress distribution. Consequently, the risk of premature buckling and failure under compressive loading is significantly reduced, ensuring improved structural integrity and durability. The finite element simulation results presented in this study align well with the experimental findings, with a maximum error of no more than 10.68%. In conclusion, this work provides reliable guidance for the optimal patch repair of composite structures and lays a solid foundation for the practical application of patch repairs in engineering.

Optimizing the design of Ceramic Composite Armor Systems (CCASs) is crucial for liberating redundant design space and enhancing ballistic performance. However, existing solution frameworks still exhibit deficiencies in handling multi-constrained optimization, particularly regarding surrogate model generalization and the nonlinearity and non-convexity of solution algorithms, leading to suboptimal accuracy and efficiency. This study proposes a novel Response Surface Methodology–Adaptive Moment Estimation (RSM-Adam) framework to address these challenges. The developed RSM surrogate model integrates key CCAS failure characteristics, such as structural deformation, fiber/matrix failure and interfacial debonding/delamination into the optimization analysis using few finite element analysis (FEA). This approach overcomes the limitation of conventional theoretical models that focus solely on ballistic performance, establishing a foundation for a generalized multi-constrained optimization model. Meanwhile, an improved Adam method incorporating a cosine step-size adjustment strategy demonstrates superior capability in handling nonlinearity and non-convexity during iteration compared to conventional algorithms like the Simulated Annealing Algorithm (SAA), Particle Swarm Optimization (PSO), and Genetic Algorithm (GA). It achieves over 60% reduction in computational error compared with conventional intelligent algorithms, while maintaining a computational cost comparable to or lower than most of them, proving highly effective and efficient for complex multi-constrained models. The rationality and accuracy of the RSM-Adam framework are validated through ballistic testing and FEA of an Al₂O₃/Carbon Fiber (CF)/Aramid Fiber (AF) composite armor sample, with systematic analysis of the influence of key framework parameters on optimization outcomes. It is also confirmed that the proposed RSM-Adam framework provides a practical, widely applicable, and engineering-valuable solution for the multi-constrained optimal design of the CCAS.