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Nano-Material Armor

Improved nano-properties include reduced weight, higher strength, increased durability, increased reactivity, and the ability to vary or "tune" certain properties. These properties allow for great potential when it comes to reducing the weight of Soldier equipment and improving lethality and survivability.

In 2005 the Israeli company ApNano was working on an application of their technology to shielding and protection. In research lead by Prof. Yan Qiu Zhu of the School of Mechanical, Materials and Manufacturing Engineering at the University of Nottingham, England, a sample of the ApNano material was subjected to severe shocks generated by a steel projectile traveling at velocities of up to 1.5 km/second. The material withstood the shock pressures generated by the impacts of up to 250 tons per square centimeter. This is approximately equivalent to dropping four diesel locomotives onto an area the size of ones fingernail. During the test the material proved to be so strong that after the impact the samples remained essentially identical compared to the original material. Additionally, a recent study by Prof. J. M. Martin from Ecole Centrale de Lyon in France tested the new material under isostatic pressure and found it to be stable up to at least 350 tons/cm2.

Fullerenes are a new form of carbon, other forms being diamond, graphite and coal. They are molecules composed entirely of carbon, taking the form of a hollow sphere, ellipsoid, or tube. Spherical fullerenes are sometimes called buckyballs, while cylindrical fullerenes are called buckytubes or nanotubes. Buckyballs are named after R. Buckminster Fuller, architect of the geodesic dome that he designed for the 1967 Montreal World Exhibition. IF materials are Fullerene-like materials but instead of being composed out of carbon they can be created from various other inorganic elements.

Tungsten Disulfide (WS2), in contrast to organic Fullerenes, is easier and much less expensive to produce, is chemically stable and is less reactive and consequently less flammable. Organic Fullerenes are also considered to be highly toxic while IF materials have been tested extensively and deemed safe. Tungsten Disulfide is relatively heavy and for that reason ApNano experimented with other materials such as Titanium Disulfide which is at least four times lighter and is expected to perform even better than Tungsten Disulfide against shock waves.

One of the most interesting new IF properties discovered by ApNano is its extremely high degree of shock absorbing ability. Shock absorbing materials are commonly used in impact resistant applications such as ballistic protection personal body armor, bullet proof vests, vehicle armor, shields, helmets, and protective enclosures. The new Tungsten based IF material has up to twice the strength of the best impact resistant materials currently used in protective armor applications such as boron carbide and silicon carbide, and are over 5 times stronger than steel.

In 2016 a group of Army inventors received patent 9,211,586 for designing a new nanocomposite as well as developing a method to manufacture it. A non-faceted nanoparticle reinforced metal matrix composite have increased ductility, while maintaining strength. In particular, a non-faceted nanoparticle reinforced metal matrix composite may be comprised of spherical or ellipsoidal shaped (non-faceted) nanoparticles comprising one or more of boron carbide, titanium diboride, silicon nitride, alumina and boron nitride, and a nanostructured matrix composite comprised of one or more metals and/or metal alloys.

The well-established ‘Hall Petch’ relationship states that as the grain size in a material decreases, the strength increases. Unfortunately, as the strength increases, the ductility decreases. This is what is known as an inverse relationship — one goes up, the other down — like a lever. The innovation incorporated boron carbide nanopowder into a nanomaterial as a reinforcing, or strengthening, phase along with some coarse grained material, which enhanced the ductility. The simultaneous addition of these materials to the already nano-structured aluminum led to substantial increases in strength, while maintaining ductility. The new nanocomposite is comprised of non-faceted nanoparticles reinforcing a nanostructured metal matrix. This means that instead of having a large particle with many flat surfaces, similar to a gemstone, the submicron particle portrays a spherical surface that is surrounded by aluminum. The nanocomposite also has a much smaller grain size than what is currently used. For instance, Small Armor Protective Inserts, ceramic plates that are used in items like body armor, are typically more than 10 microns in grain size. As a result, this new nanocomposite solves an ongoing challenge with nanostructured materials: the loss of ductility, when the material can deform without breaking.

For the warfighter, this means that engineers and scientists could reduce the weight of current vehicular armor materials by using a less dense ceramic material. The average Soldier wears about 37 pounds of ceramic armor on his or her body. The team’s new nanocomposite could potentially help to bring that number down below 30 pounds at a minimum.

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