Ballistic composites are meeting demands for protective gear, equipment and shelter.
Composites manufacturers are continually looking for ways to enhance the performance of materials, making them thinner, lighter and stronger. But producers of ballistic composites have a much greater incentive for improvement than most: the material changes they make can literally save lives.
The most common types of composite ballistic materials used today are para-aramids (aromatic polyamides) such as Kevlar® and Twaron® and the newer high-molecular weight polyethylene (HMWPE) or ultra-high-molecular weight polyethylene (UHMWPE) such as Dyneema® and Spectra®. Military and police forces, the main customers for ballistic composites, have used one or both types for helmets, body armor, vests and shields and for armor components on tanks, helicopters, planes and other vehicles.
Ballistic composites provide significant performance enhancement and weight reduction over metal ballistic materials in such applications. “When you replace metal with a non-metallic system like a standard polymer matrix composite material you’re significantly lessening the likelihood of degradation due to corrosion in extreme environments,” says Steve Taulbee, general engineer in the Office of the Director for the Weapons and Materials Research Directorate at the U.S. Army Research Laboratory at Aberdeen, Proving Ground, Md.
The Evolution of Military Ballistics
The U.S. Army started investigating the potential of composite materials for ballistic applications (specifically Kevlar vests) at the end of the Vietnam War. In 1989, the Army fielded its first composite helmet in combat in Panama, made from a Kevlar fiber hardened by a thermoset resin matrix. The most recent iteration is the enhanced combat helmet (ECH), made with UHMWPE. “It improved ballistic protection by 35 percent over any and all of the previous generations of the Kevlar helmet,” says Taulbee.
The Army is currently researching the use of UHMWPEs to reduce the weight of next-generation military aircraft, pursuing 3-D weaving with several industry partners, including Albany Engineered Composites and T.E.A.M. Inc.
With military aircraft, there is a lot of pressure to reduce the weight of the armor without compromising protection, says Nick Baird, director of sales and marketing at Permali Gloucester Ltd. The company uses aramids, glass fibers and UHMWPEs to create ballistic protection for helicopters like the CH-47 Chinook and the AW101 Merlin. The materials have to resist vibration and crash loads and meet flammability specifications as well.
Permali is investing heavily in the development of molded composite structures to provide mine and blast protection for vehicles. “We have shown that the right composite solution outperforms steel by resisting higher blast loads, by having lower dynamic deflection and by exhibiting ‘graceful degradation,’’’ says Baird. “Composites show very progressive behavior as you increase the blast loading, whereas steel fabrications tend to fail suddenly and catastrophically as you exceed their threshold.” In one case, Permali replaced a steel roof on a vehicle with a stronger, stiffer composite roof, providing a rigid and stable platform for a roof-mounted remote weapon station.