*2.2.1 Self-healing efficiency*

The self-healing efficiency (η) is a crucial metric used to assess the restorative capabilities of a material following a damage and healing cycle. It quantifies the degree of functionality restoration, and there are several definitions of healing efficiency, with the most widely employed formula being *η = Phealed/Poriginal*. The parameter "*P*" can encompass a range of characteristics based on the research focus, including ultimate tensile strength, elongation, fracture toughness, Young's modulus values, and other properties that pertain to electrical, thermal, optical, or capacityrelated indices. For instance, carbon/epoxy composites with self-healing capabilities, achieved through the incorporation of healing agents, exhibit a notable healing efficiency of 62% [40]. This efficiency is determined based on the changes observed in flexural strength. Benazzo et al. [41] engineered a high-performance epoxy vitrimer for deployment as the matrix phase within fiber-glass composites featuring the integration of Fiber Bragg Grating (FBG) sensors. The investigation showcased that laminates possessing a greater proportion of dynamic crosslinkers manifest enhanced reparative capabilities. Notably, during the initial healing cycle, the average and maximum recorded healing efficiencies, computed with respect to critical fracture toughness, were determined to be 89% and 95%, respectively. A higher healing efficiency enhances the material's self-healing ability, resulting in an extended service lifetime that aligns with specific application requirements.
