Study on Mode II Interfacial Fracture Toughness and Self‐Healing Efficiency of Self‐Healing Carbon Fiber Reinforced Polymer/Polyvinyl Chloride Foam Composite Sandwich Structures

Self‐healing adhesive films (SHAFs) by embedding microcapsules containing epoxy and microcapsules containing hardener within an adhesive matrix are developed in this study. These SHAFs are engineered into carbon fiber reinforced polymer (CFRP)‐to‐ polyvinyl chloride (PVC) foam interfaces in composite sandwich structures to enable simultaneous interfacial toughening and autonomous crack repair. The effect of microcapsule content on mode II interfacial fracture toughness and self‐healing efficiency is studied using end‐notched flexure tests. The results demonstrate that the SHAFs containing 18.75 wt% microcapsules lead to a remarkable 103.95% improvement in mode II interfacial fracture toughness compared to conventional CFRP/PVC composite sandwich structures without the SHAFs, while also achieving a healing efficiency of 69.95%. A comprehensive analysis of crack deflection, microcapsule rupture‐triggered healing agent release, and interfacial rebonding mechanisms demonstrates the synergistic toughening‐healing behavior. This work establishes a scalable strategy for engineering high‐performance self‐healing composite sandwiches with dual functionality.