# Optimization of Composite Material Repair Patch Shape Based on Strength Analysis
## 2 Research Status on Shape Selection and Strength Analysis of Repaired Composite Laminates  
Researchers have conducted extensive studies on the grinding adhesive repair process and repair parameters of composite materials. Among them, much attention has been paid to the influence of factors such as patch size, patch thickness, adhesive layer thickness, grinding hole inclination angle, and curing process parameters on the strength of repaired composite materials. Some of the literature also involves evaluating the effects of different patch shapes on repaired components by analyzing failure strength, fatigue life, and other factors. In recent years, there have been studies on the shape of patches used in composite material repairs. For example, [PERSON] et al. [3] evaluated the damage components of small openings repaired with patches of different shapes using a progressive damage model, concluding that square patches yielded better results than other shapes. [PERSON] [4], [PERSON] [5], and others repaired aircraft aluminum alloy structural components with patches of different shapes, analyzing the pros and cons of various patch shapes based on considerations such as reducing stress concentration and maximum shear stress within the adhesive layer. [PERSON] [6] and others repaired composite material cracks using patches of four different shapes and obtained the bond strength of patches of different shapes using four-point bending tests. In the field of research on the failure strength of composite structural components: [PERSON]. [PERSON] et al. [7] proposed the prospects and challenges of adhesive repair. [PERSON] [8] studied the fatigue crack repair method of aircraft primary load-bearing structural components and analyzed the advantages of the repair method from three aspects: fatigue strength of patches, environmental usage, and intelligent monitoring. [PERSON], [PERSON] [9], [PERSON] [10], and others introduced an experimental study on the residual strength and fatigue crack propagation life of glass epoxy composite patched repairs on edge-cracked aluminum specimens and judged the effectiveness of the repair through static strength and fatigue tests. [PERSON] [11] studied the influence of drilling holes in glass fiber-reinforced composite materials, including the effect of adding square inserts below the outermost layer in the stacking sequence on the strength of laminates before and after post-curing. [PERSON] [12] et al. conducted full-scale composite repair static tensile experiments to determine the strength of components after repair. [PERSON] [13], [PERSON] [14], [PERSON] [15], [PERSON] [16], and others experimentally verified and finite-element modeled the effects of layup angle, grinding angle, patch size, and additional ply on the adhesive strength, interlaminar shear force, stress concentration factor, and fatigue strength of composite repairs. Most of these experiments and modeling were conducted using simplified inclined grinding repair models. [PERSON] [17], [PERSON] [18], et al., conducted full-scale simulation and modeling analysis on the influence of the size and shape of composite patch on the strength after composite repair. [PERSON] [17] used the 3D Hashin failure criterion to predict the strength of repaired composite structures, while [PERSON] [18] proposed a damage zone model based on the equivalent [PERSON] strain criterion and used this model as a criterion for failure; they respectively proposed better repair patch shapes under their theoretical systems, but the results were not consistent. [PERSON], [PERSON] [19], and others introduced a new bolt/pin connection method for composite repair and introduced a new patch reinforcement to achieve it. The advantages of this connection method were analyzed through static loading and fatigue experiments.