Aircraft manufacturing comes out of the oven

Composite materials for aircraft wings and fuselages are typically manufactured in large, industrial-sized ovens. Multiple polymer layers are blasted with 750°F of heat and solidified to form a solid, resilient material. Considerable energy is required to heat the oven, the gas around it, and the actual composite.

Aerospace engineers at Massachusetts Institute of Technology (MIT) have developed a carbon nanotube (CNT) film that can heat and solidify a composite without ovens. When connected to an electrical power source and wrapped over a multilayer polymer composite, the heated film stimulates the polymer to solidify.

Engineers tested the film on a common carbon-fiber material used in aircraft components, finding that it created a composite as strong as that manufactured in conventional ovens – using only 1% of the energy.

The new approach may offer a more direct, energy-saving method for manufacturing virtually any industrial composite, says Brian L. Wardle, an associate professor of aeronautics and astronautics at MIT.

“Typically, if you’re going to cook a fuselage for an Airbus A350 or Boeing 787, you’ve got about a four-story oven. That’s tens of millions of dollars in infrastructure that you don’t need,” Wardle says. “Our technique puts the heat where it is needed, in direct contact with the part being assembled. Think of it as a self-heating pizza. Instead of an oven, you just plug the pizza into the wall, and it cooks itself.”

Carbon nanotubes – a fraction of a human hair’s diameter and negligible in weight – heat efficiently when exposed to an electric current. The film fuses with the underlying polymer layers and meshes with the composite.

In initial experiments, the researchers investigated the film’s potential to fuse two types of aerospace-grade composite typically used in aircraft wings and fuselages. Normally the material, composed of about 16 layers, is solidified – cross-linked – in a high-temperature industrial oven.

The researchers manufactured a small square of CNT film, placed it over a square of Cycom 5320-1 composite, connected electrodes to the film, and then applied a current to heat both the film and the underlying polymer. Both the traditional oven-based and CNT methods generated composites with similar cross-linking density.

The team is working with industrial partners to find ways to scale up the technology to manufacture composites large enough to make airplane fuselages and wings.

The new technique may also open the door to smaller firms that lack access to large industrial ovens.

“Smaller companies that want to fabricate composite parts may be able to do so without investing in large ovens or outsourcing,” says Gregory Odegard, a professor of computational mechanics at Michigan Technological University, who was not involved in the research.

This research was funded in part by Airbus Group, Boeing, Embraer, Lockheed Martin, Saab AB, TohoTenax, ANSYS Inc., the Air Force Research Laboratory at Wright-Patterson Air Force Base, and the U.S. Army Research Office.

MIT Energy Initiative
http://mitei.mit.edu