Air Force considers applications of 'jamming' model Published July 25, 2008 By Molly Lachance Air Force Office of Scientific Research ARLINGTON, Va. -- Granular fluids, like salt or sand, and viscous liquids, like toothpaste or wood glue, can behave like liquids or solids depending on certain conditions. When these fragile materials stop flowing, scientists refer to the transition as "jamming". With funding from the Air Force Office of Scientific Research, Dr. Pirouz Kavehpour and his team of researchers at the UCLA Henry Samueli School of Engineering and Applied Science have developed a special system called a Tribo-rheometer for testing their new theoretical model to predict jamming behaviors in fragile materials. Air Force officials are interested in the benefits this model will have on new materials that enhance Department of Defense systems. These materials could range from a new family of lubricants for extreme environment application to a new generation of impact-resistant shields. Fragile materials share common jamming behaviors, but until now, researchers have been unable to establish a common mechanism among the different types. By using a thermodynamic approach, the researchers at UCLA can now predict jamming behavior of numerous materials using a single model. The team began by focusing on the behavior of dry sand. Dr. Kavehpour and his team used an existing model, but introduced a non-thermal temperature that measures the fluffiness of the granular material. The temperature variable also made sense when studying viscous liquids, which when cooled become resistant to flow. Dr. Kavehpour's team plans to use the model for a variety of actual applications in the commercial and defense industries. Currently the team is working with the Air Force Research Laboratory to study the behavior of a new family of durable, strong materials with potential applications of interest to the Air Force.