Rapid Consolidation and Curing of Advanced Composites with Electron Beam Irradiation

Abstract

The ‘holy grail’ of advanced thermoset composites manufacturing would combine resin infusion (mixed in situ), low-cost consolidation, and snap curing into one step. As a first step, a hybrid process that unites vacuum infusion processing (VIP), resin curing by electron beam (EB) irradiation and high pressure consolidation with specialized elastomeric tooling (SET) – referred to as VIP-EB-SET – has been proposed. To demonstrate feasibility, a VIP-EP-SET mold set was designed to allow a flat four-ply carbon fiber preform to be infused with epoxy, consolidated with an elastomer-faced SET tool to 690 kPa and EB-cured using a 3 MeV source. Test specimens were made by drawing resin from a container through a tube into fiber preform-filled mold cavity until full wet-out was achieved, compressing the mold set with specified force in a hydraulic press and then bolting together to maintain that force, and finally exposing to a EB accelerator to cure in 10’s of seconds. Although the thick weave reinforcement fabric and part locations proved troublesome, three parts were successfully made for each combination of two different infusion resins, one with a cationic and the other with a free radical chemistry, and two different consolidation pressures, 91 kPa (full vacuum) and 690 kPa (typical autoclave pressure). Two other parts were also made by wet layup for comparison purposes. Preliminary part quality metrics measured included thickness, maximum flexural stress and flexural secant modulus. As expected, high pressure consolidation with a snap cure system dramatically reduced final part thickness. Interesting, consolidation resulted in significant improvement for part strength and stiffness for the cationic resin but not so for the free radical resin. Although feasibility of the VIP-EB-SET process has clearly been demonstrated, future work will involve more quality metric measurements for existing parts, understanding the role of resin chemistry in this new process, and designing and testing for a 3D part shape of commercial importance.