This project looks at new ways to protect materials and personnel from the damaging or lethal effects of shock waves. There are many ways to do this. Many methods involve materials with high shear strength. When a projectile hits such a material, it stretches away from the impact site and does not allow the projectile to penetrate. In fact one of the ways new protective materials are tested involves finding how thick the material must be to resist penetration.
We are studying multifunctional materials that resist shocks and projectiles using multiple mechanisms. Part of this research effort involves new ways of studying shocked materials by post-mortem examination and also by directly measuring the strength of the incident and transmitted shock to measure shock wave energy absorption to understand how the material converts shock energy into heat.
The material we studied the most belongs to a class of materials called metal-organic frameworks (MOFs). MOFs consist of an array of metal atoms with organic linkers to form a nanoporous material. MOFs can attenuate shock waves in three ways. First the MOF consists of a loose bed of crystals, which attenuates by powder compaction. (Think of hiding behind a sandbag when someone is shooting at you). Second the nanoporous MOF unit cell can collapse (Think of hiding behind a foam mattress). Finally, pore collapse breaks the linker-atom chemical bonds and possibly also linker bonds, using the shock energy in endothermic chemistries.