Developing Energy Absorbing Composites to Counter High Velocity Impact

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IDGA: How can aspects of velocity be defeated?

KN: If you look at the dynamic equation of motion and equilibrium, you will see that damping is the most important factor in order to defeat the velocity. Therefore, we are building an advanced network of dampers and stiffeners in order to slow down and then stop the high velocity impact effect.

It is also the first law of thermodynamics--that is, the conservation of energy principle. We convert kinetic energy to thermal and strain energy.

IDGA: What are the components of that network of dampers and stiffeners?

KN: We have over 26 layers in the armor. These layers are metal, fabric, polymer, ceramic, and so on.

IDGA: At IDGA’s February Armor conference, you’ll be discussing overcoming the armor piercing penetration effect—how is that achieved?  Is it a function of reducing velocity?

KN: In order to defeat the armor piercing effect of .50 caliber armor piercing bullet, we have to create conic fracture in some layers to decrease effective penetration stresses.

Conic fracture are characteristics of some materials, particularly fragile materials. When we put some of these materials in compression testing in the lab, they will break at 45 degrees diagonal if it was a cubic sample. Now, when we impact it with a high velocity bullet it breaks and the broken part looks like a pyramid with the top nose (narrow point) located at the contact point.

IDGA:  Does the impact from explosives require a different approach as it relates to Armor?

KN: We take care of the blast impact differently. We build the trampoline effect. This way, the armor flexes in order to absorb most of the shock wave kinetic energy as strain energy density. Basically conversion of kinetic energy into strain energy. We will also have some release chamber to flow energy through the armor. We also burn some layers in order to   convert kinetic energy to thermal energy. All this conversion is happening in .001 second and that is very important.

Dr.  Khosrow “Nema” Nematollahi  will be speaking at IDGA’s 6^thAnnual Military Armor Protection conference, to be held from Feb. 27-29, 2012.  For more information on the event, visit www.militaryarmorprotection.com, or call 1-800-882-8684.

Dr. Nema received his Ph.D. in Structural mechanics in May 1983 from Purdue University College of engineering in West Lafayette Indiana. He has been associate faculty of mechanical engineering at Purdue University School of engineering, Indianapolis since 1997. After graduating from Purdue University, he was principal engineer in the nuclear power industry for about two years at Impell and Surgent & Lundy Corporations.

He founded Modern Computer Aided Engineering Inc. (MCAE) in 1984 to develop advanced finite element analysis system. He is currently chairman of CAE-net.com Inc. He has been conducting research in thermal management system development for electric vehicle batteries and Grid Energy Storage (GES) systems in collaboration with ENER1 Inc for over a year.