At NC State University, a composite metal foam has been created which is resilient enough to keep from the force of a bullet, thereby breaking up into tiny particles upon impact. The foam will possibly be implemented into aerospace, automotive, and military applications and is lighter as compared to steel metal plating.
Afsaneh Rabiei, a professor of mechanical and aerospace engineering at NC State, started the development of the foam which mostly contains steel five years ago. Check out the incredibly tough characteristics of the CMF as a 7.62 x 63 millimetre M2 armour piercing projectile was shot directly at the metal which inflicted virtually no damage to the plate in the video above.
As per Rabiei,
“We could stop the bullet at a total thickness of less than an inch, while the indentation on the back was less than 8 millimetres. To put that in context, the NIJ standard allows up to 44 millimetres indentation in the back of an armour.”
In 2015, the results of the study conducted were published.
The CMF can be developed in several ways. Basically, in order to create the bubbles within, a gas must be introduced into the foam. As you can see in the diagram below, this can be done through the melting of the material and injection of a gas directly into the molten material. There are also other methods like adding blowing agents which evaporate at a lower temperature, off-gassing in the liquid metal. In addition to this, pressurized hydrogen can also be used. The final product is a low density, incredibly strong metallic structure.
Nonetheless, you must be aware of the fact that toughness and light materials are not the only desirable traits across all industries such as besides being enormously tough, the spacecraft and nuclear waste shipping containers are required to bear up large quantities of heat and other forms of radiation. Later that year in another study, it was unveiled that the CMF are not only amazing at blocking X-rays, gamma rays and neutron radiation, but are also capable of absorbing the immense amounts of energy in the unfortunate event of a crash.
While explaining, Rabiei said:
“This work means there’s an opportunity to use composite metal foam to develop safer systems for transporting nuclear waste, more efficient designs for spacecraft and nuclear structures, and new shielding for use in CT scanners.”
As compared to solid metallic counterparts of the same material, the metal foams are also twice as effective at blocking heat. The bubbles within the metal act as insulators, only allowing heat to be conducted through the thin walls of the metal, extending the distance the heat travels as it curves and bends around the bubbles. Additionally, the bubbles also act as shock absorbers, hence aiding the metal to be compressed more without compromising the structural integrity.
The technology behind the CMFs is only just becoming thoroughly understood. Several Industries might be improved in future applications, and made many magnitudes safer by means of the implementation of this metallic foam that is strong enough to destroy an armour piercing round.