Ballistic Loading and Structural Testing Lab
Department of Mechanical and Aerospace Engineering
Loud booms sometimes heard on the ground floor of Engineering Building III on NC State’s Centennial Campus signal successful experiments in the Ballistic Loading and Structural Testing (BLAST) Laboratory. The lab is led by Dr. Mark Pankow, an associate professor in the Department of Mechanical and Aerospace Engineering. Not factoring in a complex setup, an actual experiment lasts less than a hundredth of a second from start to finish. Pankow’s lab investigates how different materials fail in response to a wide variety of extreme loading environments. He suggests Silly Putty as an example.
“If you pull on it slowly, there’s no telling how far it will stretch. But if you pull on it quickly it snaps right in half.”
The longtime stretchy child’s toy is an elegant example of ductile-to-brittle failure transition, in which the material properties change as a function of loading rate.
Pankow’s lab has worked on projects sponsored by U.S. Army Research Laboratory, the National Science Foundation, Boeing and others. Research involves both applying impact to materials and modeling the outcome, to learn how that material reacts and if it has failed. All of the equipment in the lab simulates real-world events such as high-speed projectiles, impact from falling objects and bomb blasts. The experiments have one thing in common — they are designed to exert an extreme amount of force in a very short time frame. For example, the shock tube generates a pressure wave traveling at Mach 4 and exerts a force as high as 2,500 psi by sending a high-speed pressure load down a long tube into a containment chamber not much larger than a microwave oven. It simulates the power of a bomb blast or improvised explosive device (IED). The results are captured using multiple high-speed cameras and an array of sensors.
Modern aircraft rely heavily on composites; the BLAST Lab team identified a need to understand how those materials perform when struck by lightning. The group developed a new way to simulate a lightning strike, applying both the heat and pressure caused by a bolt to study how they cause damage, both separately and in combination. Protection systems are another important area of research for the lab. A project sponsored by an athletic apparel company focuses on protecting athletes from head injuries, by ensuring that their protection gear does not degrade on a hot day. Through the Department of Defense, the lab also works to develop techniques for evaluating the extent of injury. With a better understanding of how Kevlar in soft-body armor deforms during impact, the research findings from the BLAST Lab will inform the next generation of armor design that would mitigate impacts and reduce injuries.
The team’s work also takes them on adventures far outside the lab, most notably to perform experiments on what was once called the “Vomit Comet” operated by a company called Zero-G in Sanford, Fla. A project funded by NC Space Grant and NASA requires routine flight-testing for different types of deployable structures in a zero-gravity environment. Taking advantage of the high strength-to-weight ratio of composites, the research team developed a material to be used in the deployment of a satellite boom in space. The resulting structure can be easily unwound and deployed, then rewound, similar to a tape measure. Unlike a tape measure, though, it is rigid enough to remain stiff when deployed. Later this year, the team will travel to Florida again to continue flight testing the structures in a zero-gravity environment.