The Warsaw Voice » The Polish Science Voice » Monthly - June 3, 2015
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Smart Bulletproof Vest
A new kind of “smart” bulletproof vest developed by the Moratex Institute of Security Technologies in the central city of £ód¼ will help protect soldiers from injuries more effectively than standard vests.

Researchers around the world are trying to ensure better protection for soldiers on the battlefield. The Polish vest contains special fluids developed by engineers from the Warsaw University of Technology. The fluids, known as rheological fluids, combine the properties of fluids and solids, which means they can coagulate, have variable viscosity and hardness, and their resistance increases in response to external stimuli such as pressure and impact. The stronger the stimulus, the thicker the fluids become.

Properties like these are particularly useful in ballistics, but not all rheological fluids are suitable for use in bulletproof vests.

In the initial phase of the project, these smart fluids were used to impregnate ballistic fabrics that, folded in several layers, formed so-called soft inserts. Aiming for better protection, the researchers working on the armor added composite plates as base inserts, but the vests with the plates turned out to be too rigid, restricted the mobility of people wearing them, and were impenetrable to air. Worst of all, they only stopped projectiles with velocities of up to 365 meters per second.

The researchers eventually used a colloid of their own design—a coagulating, rheological solution with nanostructures. They also developed an innovative method to inject the special fluid into pads of hybrid elastomeric polymer, which is a plastic or a natural material that can be radically deformed without losing its resilience.

The liquid polymer is poured into two molds, one flat and the other with a regular array of projections in the shape of truncated pyramids. After the polymer solidifies, the two parts are taken out of the molds, the one with projections is filled with the rheological fluid and covered with the other, flat part. After the two parts are fixed together, the pads are placed in a mesh-like lining underneath a vest with the projections directed inwards. Empty spaces between the projections allow for body heat to be dispersed.

The rheological fluid in pads separating a soldier’s body and the base insert of the hard plates effectively absorbs the energy of bullets. The innovative vests weigh the same as traditional ones, but they are slightly thinner and more flexible. They are also better at dispersing body heat and ensure better protection against bullets than vests padded with soft ballistic fabrics.

The innovative inserts were tested in a special ballistics laboratory. Projectiles were fired at the vests with a velocity of 720 meters per second (the same as bullets from a Kalashnikov rifle), producing 10-millimeter-deep cavities in ballistic clay emulating human flesh. With traditional vests, such cavities are up to 40 millimeters deep despite the use of hard plates, soft padding and aramid fibers such as kevlar. When a bulletproof vest is forced 4 centimeters into a soldier’s body, broken ribs and internal injuries are common even when the projectile does not get through. Vests comprising ballistic plates and the new rheological pads reduce surface deformity by over 60 percent compared with traditional bulletproof vests.

The new vest has entered the stage of going commercial, drawing interest from both Polish and foreign companies.

Moratex has designed and built the new type of vest as part of the Intelligent, Passive Armor Using Rheological Fluids with Nanostructures project led by the Warsaw University of Technology’s Faculty of Materials Science and Engineering and co-financed by the European Regional Development Fund under the Innovative Economy Operational Programme. Moratex’s partners in the project also included the Military Institute of Armament Technology from Zielonka near Warsaw, which developed computer simulations of high-energy projectiles hitting composite armor containing rheological fluids.

Danuta K. Gruszczyńska