The aerospace industry is primarily using autoclaves, ovens, and microwaves for curing. The use of ovens and microwaves is somewhat confined to wet-wind missile production. Ovens are also used to cure the so-called "room-temperature- cure" composite tools. Autoclaves are the primary production curing tools for all users of prepreg.
Curing in Japan is generally performed using autoclaves. Few of the autoclaves observed by the team had fully automated and programmable controls. One item of particular interest was the close research tie between tooling and curing. Tool development makes full use of thin film pressure transducers, dielectric resin viscosity sensors, and embedded thermocouples to produce tool and cure processes which are reproducible.
Research. Autoclave research centers on improved control, critical parameter feedback transducers, tool heating, and improved vacuum bags. The Japanese are working to eliminate the need for autoclaves, researching techniques such as "cure-on-the-fly."
Tooling has more potential for improving part quality and reducing part cost than any other technological area. Tool design and part design are intimately linked. The key to success on a large majority of the composite CRAD and IRAD programs is related to tooling. Tooling for aerospace composites could be considered a benchmark activity of its own.
One of the most significant differences noted between the U.S. and Japan was in the area of tooling. This ties in with the ability to design for manufacture and assembly. Figures 1.11, 1.12, and 1.13 depict the evolution of co-cured complex components. In the U.S. we have not attained this level of unitization for many reasons, including the reluctance to rely on an untrained workforce to operate complex tooling and processes. The use of matched metal tools and totally co-cured structures in production situations was observed by the team for the first time in Japan.
Figure 1.11. Co-cured Canard Box Structure
Figure 1.12. Research Program of Sine Wave Spar and Box Beam
Figure 1.13. Wing Torque Box