Materials science professor invents stronger materials for security vests

Dr. Rick Reidy
Assistant Professor of Materials Science and Engineering
Friday, December 17, 2004

With U.S. soldiers fighting insurgents in Iraq and police officers patrolling for terrorism at home, a North Texas scientist is part of a team that is researching materials to provide greater protection from bullets and other weapons.

Rick Reidy, University of North Texas assistant professor of materials science and engineering, developed a lightweight soft body-armor vest -- a flack jacket -- that stiffens upon impact from high velocity projectiles.

Reidy says soldiers and officers are currently protected against rifles and other assault weapons by wearing vests with large, stiff steel or ceramic plates. However, these vests only fully protect the heart and lungs, he says.

Reidy says soldiers and police officers often complain that the vests are too heavy and too hot and hinder movement.

Responding to these concerns, Reidy and two professors from Johns Hopkins University, Jack Roberts and Paul Biermann, developed vests that provide more flexibility and greater protection from assault weapons, including protection on the legs. Their invention is currently in the research and development stage.

"If our patent is approved, licensing this technology to body armor manufacturers could save the lives of many soldiers and police officers," Reidy says.

Reidy says he and his fellow researchers had tested body armor in the past and were aware of their own research limitations.

"The armor we are developing will be flexible enough to allow ease of movement, but rigid enough to stop high velocity assault rifle bullets," he says. "This system can also provide comfort to the wearer through improved ventilation."

He describes the new jackets as "scale-like armor" created by overlapping ceramic composite discs within polymer layers that stiffen during impact.

"Using discs instead of ceramic plates gives more flexibility," he says. "This design of multi-layered discs is an effective way of dissipating energy."

The discs are combined in three or more overlapping layers of ceramics and metals. Each disc is approximately one-eighth of an inch thick and comprised hard materials such as alumina, tough ceramics such as zirconia, and metals that change their rigidity upon impact, including iron aluminide.

The strengths of the various materials in the discs complement each other so that when a projectile hits the vest the layers of discs within the polymer skin act together as a shock absorber, dispersing the force of impact out over a large area.

Reidy and the other researchers recently received the Johns Hopkins University Applied Physics Laboratory Invention of the Year for Physical Science.

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