The design of ballistic materials presents challenges familiar to any composites manufacturer. Producers must assess the environment where the finished product will be used: operating temperature, chemical resistance, fire resistance and smoke and toxic fume emissions. They must consider structural requirements; for example, will a composite armor panel need to support the weight of other attached equipment? How will they attach composite armor to a platform? How will they avoid ballistic weaknesses at panel joins and corners?
Ballistic composites must also provide protection against a wide variety of threats. Vests may have to deflect bullets from many different types of guns, while armored vehicles must be able to withstand projectiles, roadside bombs and shells fired from tanks. Each type of threat interacts with composite materials in a different way.
“Different composite ballistic materials offer different trade-offs between these sometimes conflicting issues, so it is crucial to fully understand and appreciate the merits and performance of all the material choices available,” says Baird.
Taulbee notes that one of the biggest challenges has been coming up with composite panels that can provide the required levels of toughness, fracture resistance and ballistic protection without delaminating when struck by bullets.
Adapting New Technologies
Some military forces are experimenting with incorporating multifunctional ballistic materials into the protective equipment that soldiers wear. Conductive materials could someday monitor a soldier’s heart rate or streamline communications. “If you could build the antenna communications system directly into [a composite vest] it could have a much sleeker design and be much lighter weight,” says Wagner. Reducing the bulk of the gear that soldiers carry minimizes their profile so they are harder to target and reduces their risk of getting caught on any obstacles.
Companies are also investigating how nano-technology could enhance the ballistic properties of composite materials. “One of the most promising classes is graphene – a 2-D, carbon-based nanomaterial,” says Taulbee. Because the carbon layer is so thin – almost at the level of atoms – researchers can control and engineer its properties. He predicts that in the long term, ballistic materials made with graphene could be “10 times the strength of steel and 10 times lighter than steel.”
ANF Technologies has developed a patented process for dispersing aluminum oxide nanofibers – brand name Nafen™ – into various resin systems, including epoxies, polyurethanes and phenolic resins. Nanosilica, carbon nanotubes and some other nanomaterials can be difficult to disperse because they have a tendency to agglomerate, according to Tim Ferland, ANF Technologies’ business development manager. Nafen is different, however, because it is not produced through high-energy electrospinning, but grown off the surface of molten aluminum.