Recent developments in thermoset curing methods

There is ongoing interest in the replacement of energy-intensive thermal curing of thermosetting composites by radiation curing methods. These include curing by gamma-rays, electron beams (EBs), ultra-violet (UV) light, and microwaves. In this short review, the pros and cons of the main radiation curing routes are described in comparison to thermal cure. Issues that will dictate the choice of curing method include the penetration depth of the radiation, capital equipment considerations, and health and safety. EB curing has a number of potential advantages over thermal cure, but is limited to specific types of resin, e.g. cationic curing epoxy resins. These often differ in terms of final properties from the usual resins qualified for aerospace applications. UV cure is limited to relatively thin and UV-transparent sections. Microwaves are attractive for pultrusion applications, but have a major limitation in the inability to use metal tooling. Although a range of applications of radiation curing have been evaluated, the widespread use of such technologies in aerospace is still some way off and may be limited to niche markets for the foreseeable future.