Lightweight Foam-Based Vehicular Armor for Mine Blast Protection

Open-cell foams offer several unique mechanisms that can be used to defeat the threat posed by mine blast effects. The initial shock wave reaching the armor is by far the greatest threat, and dissipating the energy of this shock wave is the goal of the proposed work. The first mechanism relies on the cellular structure of the open-cell foam itself. Because the foam is essentially a two-phase system, and each phase has a different sonic velocity, the incident shock wave will be diffused by the foam structure. This will decrease the amount of blast energy under the curve and the peak energy delivery rate. By using a high-strength, ductile metal foam, a material far stronger than the aluminum foams tested in the past, additional blast energy will be absorbed via crushing. Furthermore, by filling the voids of the foam with an endothermic, energy-absorbing material, even greater energy-absorbing capability is added to the system. If the endothermic polymeric filler is chosen such that it behaves like a high-viscosity fluid at high shear rates, the overpressure from the blast wave will cause it to flow through the foam, and viscous dissipation will remove additional energy from the blast. Finally, by incorporating nanoparticles into the filler, additional energy can be extracted from the shock via viscous dissipation from the particles moving through the filler. Grading the mechanical properties of the system will further attenuate the blast wave and mitigate reflections and inadvertent amplification of the blast. The net effect will be a significant reduction in the level of energy transmitted to the underlying structure, and that energy will be transmitted at a slower, more sustainable level. By combining all of these mechanisms into a single lightweight system, ground vehicles will enjoy increased survivability and mobility because of the decreased armor weight. With a 1" thick slab of foam and lightweight filler, the areal density will be less than that of a 0.17" thick sheet of steel. The proposed system also offers the potential to incorporate traditional ballistic/fragment protection approaches by using a ceramic or a ceramic/metal laminate as one of the facesheets covering the foam.