A knife is another story. It has a cutting edge — in addition to a pointed tip — and is completely different from a spike or bullet.
"Unfortunately, there's little synergy," Chiou says. "When you try to have one vest provide all the protection an officer needs, the weight just adds up."
It's a challenge in research and development, yet multi-threat solutions are possible. One Kevlar ballistic material can be combined with another to defeat more than one threat, and DuPont does this in its Kevlar Correctional, which provides protection from bullets, shanks, awls, spikes and handmade knives. When a weapon made to stab an officer strikes the 200-denier Kevlar Correctional material, the fibers dissipate the energy and restrict the weapon from pushing the fibers apart. The technology helps vests meet NIJ Standard 0115.00.More protection for more threats
Chiou predicts different threats will continue to evolve.
Looking back to the 1980s, there was a different type of threat, which is addressed in NIJ Level I, Chiou says, noting today the .22-caliber is almost obsolete at the street level. Last year, he points out about 50 percent of NIJ vest purchases were Level IIIA.
"People are looking for a higher level of protection, Chiou says, "and we can anticipate the same in the future." He adds, "people are also looking for multiple threat protection. That means a vest must not only be able to protect against a bullet, it must also protect against knives and spikes, as well as chem/bio hazards."
More and more, DuPont is addressing the safety of police officers in broader terms. DuPont is in a unique position to protect first responders from thermal, chemical and biological threats with its Nomex, Tychem and Tyvek brands. The rigid molecular structure of Kevlar Correctional offers thermal stability and high resistance to many dangers, including thermal hazards more than 500 degrees Fahrenheit.
Chiou envisions that in the future, ballistic vests will have smarter fibers to help regulate body temperatures so a police officer working in Texas' summer heat, for example, will be able to comfortably wear a vest for an entire shift. A system of sensors could be incorporated to communicate his vital signs, he adds.Increased protection and wear rates
As technology advances, McGonagle says body armor will become even lighter, more flexible and more comfortable. "If vests are comfortable, people will wear them," he says.
To meet the growing demand for Kevlar fiber, DuPont will invest $500 million in a multi-phase Kevlar production expansion, which will be finished in 2010. Through fiber development architecture (the art of fiber assembly), DuPont will make its high performance Kevlar an even better performer.
As different threats (bullets, knives, spikes, military fragments) require different solutions, they are defeated by a different balance of properties, including fiber strength and elongation. Yet, McGonagle says, "We find it's impossible to work only on fiber development. You have to work on architecture development as well."
Architecture is the structure in which the fiber is placed to allow it to do its job, he describes. Fiber alone cannot stop a bullet or knife.
Chiou compares fibers to bricks used to build houses. "We are able to make a different type of brick by modifying the fine structure of the Kevlar fiber," he says. But the architecture, or how the fibers are assembled, is important too. Taking the weight out of ballistic solutions also can allow weight to be included for other protection elements, he adds.
McGonagle points out road traffic accidents have been causing more police officer fatalities than shootings. This happens, in part, because of better ballistic vest technology and increased wear.
Unfortunately, vest wear rates are not 100 percent, he says. DuPont continues working with the International Association of Chiefs of Police (IACP) to promote vest wear. In 1987, the IACP/DuPont Kevlar Survivors' Club was formed. Since then, more than 3,000 individuals working in law enforcement have survived ballistic and non-ballistic incidents because they were wearing body armor. (For more information, see www2.dupont.com.)