Microencapsulated resin mineral composites (MRMC) are widely used in the infrastructure industry for their ability to intelligently detect and autonomously repair the microcracks, whereas the interactions between microcracks and components of self-healing composites have not been well understood. To reveal the damage behavior of MRMC, a mesoscopic fracture model of the self-healing composites was established based on the cohesive element, the variation rule of damage characteristics was analyzed at the mesoscopic level, and the effect mechanism of the microcracks was elucidated. The results show that the rupture behavior of the microcapsules is influenced by the relative positions of the components, and the mesoscopic damage of the self-healing composites is dominated by the tensile cracks. Increasing the microcapsule size can reduce the curvature of the microcrack path, reducing the rupture probability of microcapsules. The relationship between the mechanical properties of the materials and their repair potential is balanced when the volume fraction of microcapsules is at 5%. The effect mechanism of microcracks within the material is influenced by the geometrical characteristics of the aggregate and its spatial distribution pattern. The smaller the aggregate volume fraction and aggregate size is, the greater the randomness of the propagation path of microcrack is. These findings contribute to a better understanding of the intelligent repair behavior of MRMC, thereby providing technical support to improve the serviceability of the structural parts.

Purpose—The flexspline of a harmonic drive constitutes a thin-walled structure with discontinuous gear rim and cylinder configuration, where cyclic stresses induce stress concentration, followed by crack initiation, propagation, and ultimately fatigue failure. This paper reviews advancements in understanding its mechanical properties and fatigue failure mechanisms, aiming to establish a foundation for enhancing operational longevity and guiding future research. Design/Methodology/Approach—The study integrates meshing theory, tooth shape parameters, cylinder stress influencers, and assembly/meshing stress considerations. Theoretical analysis, finite element simulations, and experimental methods are employed to examine stress patterns and fatigue dynamics. Structural parameters and tooth profiles are systematically analyzed for their impact on stress distribution and fatigue life. Findings—Flexspline fatigue failure arises from tooth root stress concentration and cylinder bending stress accumulation. The double-circular-arc tooth profile boosts load capacity by 35% relative to the involute profile, yet demands high-precision machining to preserve meshing performance. Increasing cylinder length mitigates stress concentration but reduces torsional stiffness, while optimized root fillet radii can lower the stress concentration coefficient by 28%. Assembly interference and meshing contact stress accelerate crack initiation, as validated by transient dynamics simulations. Surface strengthening processes (e.g., shot peening) enhance fatigue life by up to 66% through residual compressive stress regulation. Originality/Value—This paper synthesizes multi-scale research on flexspline design, structural optimization, and fatigue mechanisms, proposing novel approaches such as “manufacturability-oriented optimization” and digital twin-driven monitoring. By linking dynamic loads, material properties, and geometric parameters, it bridges theoretical gaps and provides actionable insights for high-precision harmonic drives in robotics and aerospace, advancing reliability in precision transmission systems.