An extrinsic welding method for thermosetting composites: Strong and repeatable

Joining thermosetting composites plays a substantial role in modern technologies while remaining a grand challenge. Herein we propose an extrinsic welding method to achieve strong and repeatable joining of thermosetting composites. The key point is the solvent-stimulated covalent bond exchange reactions at the welding interface. By extrinsically introducing a hydroxyl-terminated solvent to break and reform ester bonds across the welding interface of epoxy composites, we are able to covalently join the composites, leading to appreciable joining strength. The appropriate immersion time and welding time alongside efficient surface repairing can promote the joining strength of welded composites.