A team of scientists at North Carolina State University has had success with making use of composite metal foams (CMFs) for stopping bullets and blocking radiation. The team has been working on coming up with a new one with the aim of having it outperform aluminum when utilized in the construction of aircraft wings.
CMFs are comprised of hollow spheres that have been made using one kind of metal and are contained within a solid matrix that is created by either using the same or a different metal. CMFs are lighter than the traditional solid metals and yet can provide with comparable strengths. The team is being led by Prof. Afsaneh Rabiel, and the latest created material is known as an infused CMF.
The latest infused CMF has been based on a steel-steel CMF, implying that both the matrix and the hollow spheres are made using stainless steel. Furthermore, by making use of a vacuum process, hydrophobic epoxy resin has been introduced to the material (it is pulled into the material). As a result of this process, the inside of the sphere gets filled with epoxy resin. The process also ensures that 88% of the smaller pores within the matrix material are filled.
The team has tested the infused CMF against the conventional aerospace aluminum to ascertain which material would perform better when utilized on the leading edge of an aircraft wing. It was concluded that the CMF performed better in three particular areas. It proved to be better at causing water to bead up and roll off instead of allowing it to cling into place. In technical jargon, the contact angle for the infused CMF was 130% higher as opposed to that of aluminum. The contact angle of a material is inversely proportional to the amount of water that clings onto the surface.
Secondly, upon blasting of insects against both materials, 60% less residue ended up getting accumulated on the infused CMF in terms of the height of accumulation and 30% less when based on area covered. Thirdly and finally, the infused CMF performed better in grit blast tests. Rabiei said, ‘Our results suggest that infused CMF may be a valuable replacement [for aluminum], 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.’
A paper on the research has been published in the journal Applied Surface Science.