Process and tooling for low cost, rapid curing of composites structures

The process described in this article is one of the few truly innovative methods of curing composites that have been developed in the last decade. The process uses a liquid, rather than the air in an oven or autoclave, to transfer heat into and away from the laminate. The process has been developed, in Australia, by Quickstep Technologies. The process involves placing the tool and uncured component in a vacuum bag and placing that in a low-pressure pressure chamber of liquid. A computer-controlled system delivers liquid from one of three storage tanks held at the cure temperature, the dwell temperature and a low temperature. Heat up rates that would normally cause an exotherm can be used as heat can be rapidly removed from the part because of the close proximity of the liquid. Because the tool is surrounded by hydrostatic pressure there are no loads imposed on the tool, which is typically a CFRP single skin with none of the usual stiffening structures. The benefits are rapid curing and lower cost tooling. A further enhancement of the process is to insulate selected areas on the part so that they solidify but do not cure. In this way two components can be brought together in another cycle and subsequently joined without the cost of adhesives and with near parent material strengths. The latest development of the process is to apply it to the resin infusion process, where it has been successfully applied using very reactive resin systems.