The U.S. Army recently set ambitious goals to further reduce the weight of body armor by 30 to 50 percent. Institute scientists therefore proposed a unique approach, one that would identify the needed properties of materials to obtain the goal, determine geometry changes that could lead to lighter weights, or use a combination of both. The approach simultaneously pursues experimentation, large-scale numerical simulations, and analytical modeling. With modern diagnostics, scientists can gather more information during the actual penetration event. The location of the front end of the projectile as it penetrates a target can be determined with X-rays.
Experiments are the final arbitrators in ballistics.
Even with today's diagnostics, there is much information scientists cannot obtain, such as how the material moves within the target, the role of various material properties in the penetration process, and the state of stress within the target. Large-scale computer codes for ballistics problems are based on the conservation of mass, momentum, and energy. Space is divided into small cells or elements, and the material is modeled with detailed equations of state and constitutive models to fully represent stress in terms of current deformed shape and deformation history. The smaller the cells or elements the space is divided into, the more accurate the simulation, but also the more time it takes to do a calculation. Metals are modeled quite well.