Multi-mode self-healing in composite materials using novel chemistry

A novel Lewis acid-catalysed self-healing system is investigated for implementation in epoxy-based fibre reinforced polymer (FRP) composite materials. The catalyst, scandium(III) triflate, is selected using a qualitative approach and subsequently embedded with pre-synthesised epoxy-solvent loaded microcapsules, into an epoxy resin. Healing is initiated when microcapsules are ruptured at the onset of crack propagation. The epoxy monomer healing agent contained within, actively undergoes ring-opening polymerisation (ROP) on contact with the locally placed catalyst, forming a new polymer to bridge the two fractured crack surfaces. Self-healing performance is quantified using tapered double cantilever beam (TDCB) epoxy resin test specimens and the effects of microcapsule loading, microcapsule content and healing temperature are all independently considered. As an initial proof of concept study, results show that a material recovery value of greater than 80% fracture strength is achieved for this novel Lewis acid-catalysed self-healing epoxy resin. The same self-healing agent system was subsequently demonstrated in a larger scale FRP component by incorporating both a microcapsule and hollow glass fibre (HGF) delivery system within an FRP laminate using a End-Notched Flexure (ENF) test configuration.