Metal foams continue to prove themselves as an extremely useful material with a number of unique properties that continue to surprise researchers and the manufacturing community. Having the ability to manufacture a material that is extremely durable, flexible and incredibly resistant to deformation and fracturing is something researchers have been after for a while now. A new kind of metal foam has been developed by researchers at North Carolina State University and this composite shows some incredible promise.

“We were looking for a light and cheap metal with a low melting point to cast around steel hollow spheres, a metal easy to play with,” said Dr. Afsaneh Rabiei, professor at the Mechanical and Aerospace Engineering Department at NC state. The main material they decided to work with ended up being aluminum.

Their work started by looking at the reasons other metal foams failed in the past. “The porosity of the metal (steel) was causing the material to fail, – There needed to be an infrastructure in place where there was an equal distribution of loading,” another statement by Rabiei. To prevent stress concentration and premature failure while still allowing the material to remain light and a potential for absorbing energy, she distributed the porosities throughout the material in a uniform manner.

The hollow spheres that can be seen throughout the metal foam helped to create the lightweight structure but by itself it didn’t have the strength the researchers were looking for. “I added a metallic matrix design to the mix,” she explains. She simplified her thought process by comparing the metal foam to a jar full of hollow spheres, she needed something to fill the gaps in between the objects to reinforce the entire structure. The way she reinforced the structure was by casting aluminum around the steel hollow spheres. “When you cast the aluminum, the steel spheres do not melt down, – The beauty of the technique is we can make the entire matrix and spheres out of the same metal such as steel, a cheaper alloy” said Rabiei.

Rabiei goes on to explain the actual make-up of this particular metal foam and why it stands out among other less resilient materials. Rabiei – “We mix, sinter and press them, creating the steel composite foam. Now we have two types of material, one includes a low melting point matrix such as aluminum with a higher melting point spheres and the other one is composed of hollow spheres and a matrix made from the same material such as steel”. The benefit of using steel and aluminum is that these materials are widely available and are extremely affordable. This helps accelerate research and development and when in use, the product can be manufactured quickly and avoid a large price tag.

Now the research team is working on bringing the composite metal foam out of the lab and begin applying it to commercial uses. Some of products that the metal foam can be used for includes, car bumpers, biomedical devices and the U.S. Army is even currently testing its potential as a bullet resistant armor. The armor would be extremely light so it could even be used to protect helicopters or aircraft which have to sacrifice protection to maintain lift and speed.

They are also currently working with investors and working alongside federal agencies to bring this material toward real-life applications which even include space shuttles and lunar explorations. This material could have a profound impact in many different fields. The availability of the materials that are used within the metal foam are helping to speed up its development and researchers expect the material to make it to market relatively soon. As research continues surrounding metal foams, the possibilities continue to expand and the unique properties of the materials continue to excite the entire manufacturing community as well as the scientist that are working with these amazing metals every day.