Blast Mitigation Through the Operation of Steering the Incoming Wave by the Use of Active Metamaterial Structure

Abstract

The current state of the technology to protect a structure, from an incoming blast wave, is to either design the structure to withstand the effects of the blast wave or to place a protective shield in between the blast wave and the structure. The goals of the shield or the protective structure are to absorb the energy of the blast wave and attenuate the damaging stresses to a level that the structure can safely withstand the stresses. This is still an active research area and researchers are seeking new materials for the shield, their strength to weight ratios, and are developing new design techniques. The objectives of this paper are very different. The goals of this paper are to seek active metamaterial structures (AMMS) to steer an incoming blast wave away from the protected structure. Foundations for new work start with the work of Veselago, in 1968, on the subject of optical or electromagnetic waves. He considered materials that have a simultaneous negative electrical permittivity and magnetic permeability and showed that it resulted in a negative refractive index. His work opened the future options for optical cloaking and perfect lenses. No such natural material existed. This work was later followed by Pendry (1996) to use metamaterials to realize Veselago’s goals. Later Pendry and others developed a transformation technique to design such metamaterials. Because the wavelengths, associated with optics were, very small Cummer and other engineers sought applications in the area of acoustic cloaking because of similarities in the areas of optical and acoustic wave propagation. For blast mitigation, the interest is in the area of solid mechanics and shock waves in solids. The wave propagation in solids is very different from optics. To start, our objective is to rely on the work done to date of elastic metamaterials and transformation of wave propagation in solids to steer the path of the shock wave. The theoretical work has resulted in changes to density and material constitutive relations. No currently existing material or metamaterial designs are available to obtain such changes of material properties. Thus, the primary objective of this paper is to present an actively controlled system called active metamaterial structure (AMMS). The AMMS can achieve such changes in density and stiffness properties, similar to the ways we have achieved and experimentally demonstrated very high damping ratios by using piezoelectric materials and piezoelectric stacks. Next steps are shock waves for which a procedure is discussed.