Bulletproof Foam Builds a Better Airplane Wing

Back in June, we watched as Composite Metal Foam (CMF) stopped armor-piercing bullets. Researchers fired a .50-caliber armor-piercing round 514 meters per second at the foam, and it bounced off.Now, researchers from North Carolina State University have a new, slightly less volatile application for the foam. Using a combination of CMF and epoxy resin, the team believes that they could revolutionize aircraft wing design. And really, anything that uses aluminum. The hybrid material is called "infused CMF." When we saw the bullet-bouncing foam, it was made up of hollow spheres of steel and titanium embedded into steel, aluminum or other alloys. The hybrid uses stainless steel spheres and a stainless steel matrix. However, they immerse the material in a hydrophobic epoxy resin and use vacuum forces to draw resin into the hollow spheres and pores in the matrix. After the process, about 88 percent of the CMF's pores are filled with resin. What I found most interesting was how they tested it. In order to stand up to aerospace-grade aluminum, they needed to see how quickly water streams off it, how well it stands up to erosion, and how well bug parts stick to it. Really.In all tests, the infused CMF performed better than aluminum — even the bug test, which not only tests the maximum height of bug residue that builds up on the material, but the total area covered in bug guts as well. It could help cut costs on future aircraft design by improving performance while cutting the all-important weight and improving fuel efficiency. And it's better on bugs.