Metal foam better than aluminum for aircraft wings, researchers say
NC State University study finds infused CMF better repeals water and bug residue at same weight as aluminum.
Called infused CMF, the foam material consists of hollow metal spheres embedded in a metallic matrix of steel, aluminum or metallic alloys. That composite is then vacuum infused with a hydrophobic resin such that approximately 90 percent of the empty space is filled.
“While infused CMF is about the same weight as aluminum, it is tougher and has other characteristics that make it more appealing from a flight performance, safety and fuel efficiency standpoint,” says Afsaneh Rabiei, a professor of mechanical and aerospace engineering at NC State and the corresponding author of a paper on the work.
To test their infused CMF, the researchers pitted it against aerospace grade aluminum to see how the materials dealt with factors that affect leading edge performance; in particular: Insect adhesion, particle wear and contact angle (i.e. how quickly water streams off of a material).
The researchers found that infused CMF had a contact angle 130% higher than aluminum and retained that advantage even after grit blasting. In addition, the foam was 60% better in regard to maximum insect residue build-up and 30% better in surface area covered.
Overall, the researchers say infused CMF retained its properties through erosion and wear, indicating that it would give leading-edge wing components a longer lifetime and reduce the costs associated with maintenance and replacement.
“Aluminum is currently the material of choice for making the leading edge of fixed-wing and rotary-wing aircraft wings,” Rabiei says. “Our results suggest that infused CMF may be a valuable replacement, offering better performance at the same weight.
“By the same token, the results suggest that we could use different materials for the matrix or spheres to create a combination that performs as well as conventional aluminum at a fraction of the weight. Either way, you’re improving performance and fuel efficiency.”