Kinetic Energy Absorbing Aerogel Composite Structures for Use in Crash of Impact Protection and Body or Vehicle Armor
Materials absorb kinetic energy by various mechanisms including plastic deformation, elastic deformation, the dynamics of fluid flow (gases or liquids) within the material and brittle fracture. Most energy absorbing materials in use today exhibit elastomeric or plastic deformation. They are typically organic materials such as polyurethanes, polyethers, polyethylene, and expanded polystyrene. Silica or silicon dioxide aerogels, on the other hand, are inorganic materials and they are prone to brittle fracture.
Researchers at The Johns Hopkins University Applied Physics Laboratory have developed a technology which makes effective use of aerogels (e.g., silicon dioxide, carbon, etc.) as absorbers of kinetic energy such as might be encountered in body armor, bomb blasts, etc. It also could be used as crash protective covers or linings in vehicles. Silica aerogels are very low density materials composed mostly of air and an intricate but fragile network of the solid material (0.1g/cubic centimeter), in which the collapse of the solid network occurs gradually, thus spreading out the force of impact over a longer time. Also, since the aerogel is an open-pored material, the air contained within the bulk of the aerogel is forced out as the material collapses. Since the pores in the aerogel are very small (20-50nm in diameter) the friction forces on the gas passing through the pores are quite high and the material will absorb a considerable amount of energy. Thus, an aerogel handles (distributes in time) impact by a collapse of its solid structure and the release of entrained gas from within the material. Another factor, because of the aerogel structure collapse under impact, there is little or no recoil (rebound) as encountered with polymers thus mitigating any reverse transfer of energy effects. The embodiment of the invention involves the sandwiching of very light crashable aerogel layers (inorganic) between more conventional elastometric (organic) fabric layers. It is envisioned that the aerogel layers are integral with the elastometric layers, but it could also be a sandwich with facing layers tethered to each other at certain points (like upholstery or ticking on a mattress). It is envisioned that the aerogel layers would be extremely thin and flexible in the macro sense and that the protective composite would consist of multilayers (1 through n).
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