Stopping bullets

NIJ 0101.06 Known simply as NIJ O6, this standard establishes minimum performance requirements and test methods for the ballistic resistance of personal body armor. The key ingredients in the NIJ 06 testing recipe are: providing adequate protection...

Manufacturers also see nanoparticle technology as a possible means to an end. Most bullet-resistant vests utilize multiple layers of Kevlar, Twaron or Dyneema fibers to stop bullets from penetrating by spreading the bullet’s force over a larger area. Even with this protection, wearers may still be left with blunt force trauma. The elasticity of nanotechnology’s carbon nanotubes may enable manufacturers to reduce blunt force trauma without increasing vest weights.

“We are looking at advancements in nanoparticle technology, which absorbs and distributes energy and seems to have some utility in bullet-resistant vest design,” says Weber.

Some like it wet

“When you get bullet-resistant materials wet, it renders them ineffective. The weave opens up and expands and puts holes or gaps in the material,” says Melissa Allerman, vice president of Sonobond Ultrasonics of West Chester, Pennsylvania.

This fact is the impetuous behind the NIJ 06 testing protocol, which requires body armor test panels to be dunked in water for 30 minutes before shot testing. “Armor manufacturers are now using ultrasonic welding to meet this requirement,” says Taylor.

Ultrasonic welding seals the ballistic panel edges without stitching to prevent water and moisture from seeping in and degrading their ballistic integrity. But it’s not to be confused with heat-sealing, says Allerman, who points out that ultrasonic welding is a completely different process.

“Heat sealing exposes an outside heat source to the material, but ultrasonic welding generates very little heat,” she explains. “It coverts electrical energy into mechanical energy when it passes through piezoelectric crystals under compression.”

Sonobond teamed with nylon manufacturers producing materials for ballistic panel outer-coverings to add a low-melt urethane coating to one side of the nylon. This coating allows manufacturers to ultrasonically weld these coverings. Currently Brookwood Companies Inc. produces the nylon used in Sonobond’s ultrasonic welding process.

Sonobond’s SeamMaster ultrasonic welding system cleanly cuts and seals the nylon’s edges in one pass. “The ultrasonic horn transmits energy to the material,” Allerman says. “It vibrates at 20,000 times a second, and excites the molecules in the thermoplastics to seal the edges.”

While Brookwood isn’t the only manufacturer of such materials, it produces the only nylon that works with Sonobond’s technology, which is utilized by most body armor manufacturers, according to Allerman.

Taylor agrees. “Not all sonic weldable materials are created equal,” he explains. “Some materials can be perceived as stiff and noisy. We were able to work with suppliers to come up with one that could be sonic welded but was a soft, pliable fabric as opposed to a rigid and stiff material.”

“We were already seam-sealing before the NIJ 06 standard came out,” adds Davis. “We switched to a new cover made by Brookwood that is ultrasonically welded. And we worked very closely with Sonobond to make sure the seams were incredibly strong.”

Threat assessment

The Golden Rule when it comes to body armor is that it should protect officers from the threat of their own bullet.

Line-of-duty deaths increased 13 percent in 2011, with 173 officers losing their lives. Sixty-eight of those officers died in firearms-related incidents and four of them died from shots fired from their own guns.

Taylor recommends agencies catalogue and monitor the threats they are removing from the street and make sure their body armor covers those threats as well. “This gives you an idea of what’s in your area,” he says. “California is going to have different special threats than Miami and New York is going to have different threats than both of them. It depends on what’s readily available.”

Manufacturers constantly adapt their designs to what Weber calls the “bullet flavor of the month.” “There are always newer and faster bullets on the market,” he explains.

Taylor agrees, noting in years past a 9mm round was a 9mm round, but as projectile technology and composites change, manufacturers have adapted their bullet-resistant offerings.

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