UNT professor invents stronger materials for security vests to protect soldiers and law enforcement personnel

Dr. Rick Reidy
Assistant Professor of Materials Science and Engineering
Wednesday, June 2, 2004

DENTON (UNT), Texas — Protecting soldiers and law enforcement personnel is more important than ever. That’s why Dr. Rick Reidy, University of North Texas assistant professor of materials science and engineering, is developing a lightweight soft body-armor vest — a flack jacket — that stiffens upon impact from high velocity projectiles.“Current protection against assault weapons such as rifles uses large stiff steel or ceramic plates inside vests,” Reidy said. “With these vests, if you get hit by a bullet from a rifle anywhere besides the heart and lungs, there is no protection. Besides the upper body, this armor can cover the legs as well.”Reidy said today soldiers and police officers wearing vests often complain they are too heavy, too hot and hinder movement. So Reidy and two professors from Johns Hopkins University, Dr. Jack Roberts and Paul Biermann, have developed vests using a different design concept. Compared to contemporary jackets, the vests will provide more flexibility and greater protection from assault weapons. 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 said.Reidy said he and his fellow researchers had tested body armor in the past and were aware of their own research limitations. “The Johns Hopkins researchers’ expertise is polymers and mine is in ceramics,” he said.“The armor we are developing will be flexible enough to allow ease of movement, but rigid enough to stop high velocity assault rifle bullets,” Reidy said. “This system can also provide comfort to the wearer through improved ventilation.”He describes the new jackets as “dragon-scale armor” made up of overlapping ceramic composite discs within polymer layers that stiffen during impact.“Using discs instead of ceramic plates gives more flexibility,” he said. “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 1/8 inch thick and made of hard materials such as alumina, tough ceramics like zirconia and strain-rate sensitive alloys — metals that change their rigidity upon impact — such as 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 2003 Invention of the Year for Physical Science. In a publication titled “Strain Rate Sensitive Flexible Armor with Laminated Composite Elements,” the scientists show how their invention of new vests will be an improvement over current flack jackets. For more information about Reidy’s research, contact him at (940) 369-7115.

UNT News Service Phone Number: (940) 565-2108