Scientists at North Carolina State University have already had success using composite metal foams (CMFs) to stop bullets and block radiation. Now, they've determined that a new one should also outperform aluminum when used in the construction of aircraft wings.
CMFs typically consist of hollow spheres made of one type of metal, contained within a solid matrix composed of either the same or a different metal. One of their biggest selling features is that they tend to be lighter than conventional solid metals, while offering comparable strength.
Developed by a team led by Prof. Afsaneh Rabiei, the new material is known as an infused CMF.
It's based around a steel-steel CMF, meaning that both the hollow spheres and the matrix are made of stainless steel. Utilizing a vacuum process, however, a hydrophobic (water-repelling) epoxy resin is pulled into the material – as a result, the resin fills the inside of the spheres, along with about 88 percent of the smaller pores within the matrix material.
The scientists tested the infused CMF alongside traditional aerospace aluminum, to see how both materials would fare when used on the leading edge of an aircraft wing. It was found that the CMF performed better, in three specific areas.
First of all, it was superior at causing water to bead up and roll off, as opposed to clinging in place. Technically-speaking, its contact angle was 130 percent higher than that of the aluminum – the lower a material's contact angle, the greater the amount of water that clings to its surface.
Secondly, when insects were blasted against both materials, less of their residue accumulated on the CMF. Numbers-wise, there was 60 percent less residue as measured by height of accumulation, and 30 percent less according to area covered.
Finally, although both materials were made rougher when subjected to grit blast tests, the CMF still came out on top, showing less degradation.
"Our results suggest that infused CMF may be a valuable replacement [for aluminum], offering better performance at the same weight," says Rabiei. "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."
A paper on the research was published this week in the journal Applied Surface Science.
Source: North Carolina State University
