“One could probably get away with less,” Tour says. “Any time you want a nanomaterial additive, the less you can use, the better.” He says the success of the experiment is based on how well the graphene nanoribbons and epoxy are blended. The better they are blended, the fewer nanoribbons you need.
After spreading the coating, the team applied a small voltage to the blade. Through Joule heating, the coating delivered electrothermal heat to the surface of the blade and successfully melted the ice. The researchers reported that the composite withstood heat higher than 200 F and remained strong even at 600 F.
However, Tour says in the event of an actual flight, the GNR-epoxy composite wouldn’t need to reach those temperatures. For wings or blades in motion, the naturally-occurring thin layer of water between the heated composite and the blade surface is enough to loosen ice and have it fall off without completely melting the ice.
But it is not as simple as just applying the blended materials and cranking up the heat. According to Tour, he and his team had to adapt the properties of their helicopter blade, which had a metallic nickel shield. Tour says that the nickel shield shorted out any voltage applied to it, causing the current to go through the shield instead of the composite skin. The solution was to secure the nickel shield to the blade with a thin film of epoxy. Tour believes the experiment would’ve been easier had the blade been made with an epoxy-based composite.
While the experiment focused specifically on helicopter blades, Tour believes the technology could be used in any aircraft components, including the entire skin. “One wouldn’t need all these chemicals and all this other de-icing,” says Tour. “You just flick a switch and everything gets warm and de-ices. You could do this in-flight. You could turn it off in-flight and turn it back on if you start getting icing. No problem.”
Tour believes the technology has wide market potential if the right investor steps up: “I think eventually [the technology is] going to be in all of composite aircraft.”
The Shape of Things to Come
Project: Flexible shelter
School: Temple University
Principal Investigators: Andrew John Wit and Simon Kim
As the old adage goes, there are two sides to every story. However, for a group of researchers who created a 20-pound, single-occupant shelter by hand and robotically winding CFRP, there are exactly eleven sides. The shelter gets its name, rolyPOLY, because you can roll it onto any of its sides and still get inside.