Foams are having unique properties of light weight and heat resistant. This unique properties is allowing for its advanced applications in many different scenario’s. Yet being light weight, the word foam doesn’t necessarily convey strength. Seeing a bullet being exploded upon the impact with the composite metal foam certainly does.
Researchers from the North Carolina State University has created a bubble filled metallic composite which is combining the strength of the steel with the airiness and heat resistant properties of the foam. During its test with the armour piercing bullets, one inch layer of material has stopped the projectile over its tracks. It will only be allowing an indentation over the other.
Strongest metallic foam
Afsaneh Rabiei who is a professor of the Mechanical and aerospace engineering over the North Carolina State University which is claiming her version of the metallic foam to be strongest yet. Foams are mainly made up of air pockers which is making them light in weight. Rabiei is working with the composite metallic foam for quite years for understanding their unique properties. They are even trying to find out optimal configuration of materials and materials for maximizing results.
Rabiei adding to the same says, “If you look around, you will see a ton of porous materials in nature: wood, bone, leaves, a bird’s wings, anything that you want to be lightweight or have cushionability, you’ll see that it has air bubbles. It’s a waste of material and energy to carry a solid bulk of materials with you, when you can actually use something much lighter and accomplish even more.”
During her latest, which is published in International Journal of Thermal Science, Rabiei has described two different methods of making her metal foam. These both methods are relying over the hollow steel spheres for forming the “bubbles”.
Properties of metallic foam
First method of it is casting a metal with the lower melting point like that of aluminium, around the spheres. It is creating a matrix of the hollow spaces which is within. For the case of metals which are having higher melting points, spheres are packed in by means of a metallic powder. It is compressed over a process called sintering for forming a solid.
By keeping the diameter of the bubbles constant, any of the stress will be impacting them equally while increasing the strength of the material. Spherical shape of the bubbles is also conferring the shape of the bubble as well, by means of distributing the force evenly over the structure. As compared to that other metallic foams might buckle with the collapsing bubbles.
Rabiei is maintaining the structure due to the uniform nature of the components. As the spheres are filled up with air, material is also quite resistant to heat and heat-related expansions. During the latest experiments, she has even compared a block of stainless steel to the bubble-infused steel as both were heated by a 800-degree flame over one of its side.
Blocking the radiation
CMF has twice as long for reaching the 800 degrees as a solid block which is a result of the air-filled bubbles inside. Unique properties of the CMF is making them ideal for use over the body armor. Rabiei is also looking for its use in the space industry, where lightweight and durable materials are quite much in demand.
In addition to that, by adding the tungsten and vanadium to the composite, Rabiei says that CMF is also blocking out the radiation. Radiation being blocked out includes gamma rays, X rays and even the neutron radiation. This is making the material ideal for transportation of the nuclear waste. It is also increasing its utility for the case of space travel, where harmful radiation is posing a danger to the human health.
Looking at the future, Rabiei would also be testing how well her metal foam is standing up to the vibrations. It includes a property which would be carrying further benefits for the case of vehicle construction dampen sound-proofing. Ultimately, its end game includes saving the life of a person.
She says, “If I can make one person walk out of an accident because of my materials, I will have accomplished my goal.”