When a company like Boeing wants to make an airplane wing or fuselage panel, they rely on a traditional layup process and a high-heat autoclave. The autoclave applies heat and pressure to cure the multiple layers of carbon fiber inside an epoxy resin. The finished product ends up being a solid piece of carbon fiber reinforced plastic.
All of this is well and good, but autoclaves for such large parts are monstrous in and of themselves. Thanks to ongoing research at the Massachusetts Institute of Technology (MIT), the need for high heat autoclaves may be coming to an end. Researchers have found a way to cure composite materials using carbon nanotubes and electricity. Their process completely eliminates the need for ovens and autoclaves.
Building an Airplane Fuselage
The Boeing 787, now considered the crowning jewel of the Boeing fleet, relies on an extensive amount of carbon fiber throughout. Needless to say that the 787 is a huge plane. Imagine what a monumental task it must be to construct fuselage panels for this aircraft.
A single fuselage panel starts as multiple layers of carbon fiber prepregs. As Rock West Composites in Salt Lake City explains, prepregs are carbon fiber fabrics that come from the factory already impregnated with resin. They are laid into a mold until the desired level of thickness is achieved. Then the mold is placed in an autoclave where heat and pressure cure the fabric and resin.
An autoclave large enough to accommodate fuselage panels is almost as big as a small warehouse. It consumes a ton of energy doing what it does. Between energy consumption and the sheer amount of floor space needed to house an autoclave, you are talking a major financial investment for Boeing. What if they could dispense with the autoclave altogether?
The MIT Research
Back in 2015, an MIT research team began working on a process whereby they could cure composite materials without the need for an oven or autoclave. They decided to go with electricity as the curing mechanism. Making it all work relied on creating a carbon nanotube film they could wrap around the composite layers. Introducing electricity to the film generated enough heat to cure the composites in place.
Researchers dubbed their process ‘out-of-oven’ curing. With it they were able to produce composite materials that were just as strong as those made with conventional layups and autoclave curing. More importantly, they did it with 99% less energy.
Fast forward some four years and a new team of MIT researchers is working to perfect the process. Much of their focus is on improving the carbon nanotube film. By improving its performance and introducing new capabilities, they believe they can dramatically simplify composites fabricating in the aerospace industry.
Implications for Other Industries
There is no telling how close MIT researchers are to perfecting their out-of-oven process. Yet by proving it works, they have set the stage for quite a revolution in composites fabricating. The implications go way beyond aerospace manufacturing.
Think about the automotive sector. They have been chomping at the bit to incorporate more carbon fiber in their designs. What has stopped them? Cost. If car makers could produce the carbon fiber parts they want with 99% less energy and without the need for ovens and autoclaves, it’s a lot easier to justify the cost.
Taking the autoclave out of the equation changes the game entirely. Throw in an automated process for laying down carbon fiber fabrics and you have an entirely new method for producing very large composite parts at a fraction of the cost.