Damage and self-healing behaviors in aircraft-grade carbon fiber reinforced vitrimer unidirectional laminates containing exchangeable disulfide crosslinks

Given the expansion in the application of composites, their waste disposal has become a social issue, and their recycling methods have attracted considerable attention. Vitrimer, which is self-healing materials, is expected to serve as an alternative material for the matrix of structural composite materials because of its superior mechanical properties within the service temperature range similar to those of thermosetting resins, and its reprocessability and repairability at high temperatures, which is comparable to those of thermoplastic resins. This study focuses on the epoxy-based vitrimer resin and aircraft-grade carbon fiber-reinforced vitrimer (CF/vitrimer) laminates containing exchangeable disulfide crosslinks as dynamic covalent bonds, and investigates their fundamental mechanical, thermomechanical, fracture, and self-healing properties. The residual fracture toughnesses of CF/vitrimer laminates subjected to various combinations of pre- and post-healing crack opening modes and healed by different healing conditions are evaluated to demonstrate their repairability. Results reveal that the healing efficiency has significant mode-dependency, mainly attributed to the pre-healing crack opening mode and resultant fracture morphology. The developed vitrimer composite shows considerable potential as a healable structural material because of its comparable mechanical properties with conventional epoxy-based composites and its unique repairability, particularly in cracks propagated by mode II.