Metamaterials for Acoustic Cloaking

Weidlinger Associates Inc. proposes to continue the development of metamaterial-based acoustic cloaks based on its computational simulation technology developed in Phase I, and proposes to formulate and manufacture prototype cloak materials and demonstrate their effectiveness through an in-water acoustic scattering test of a cloaked cylindrical shell. Phase I explored acoustic metamaterials for acoustic cloaking of naval structures. Our approach centers on a general theory due to Norris, which describes the behavior of elastic materials with a single resistive deformation mode and five modes which are not resisted. In Phase II, we will advance the material microstructure design. The prototype material designs will be fabricated, and tested in-air to verify their properties. If ONR exercises the Phase II option, the project will conclude with in-water acoustic scattering tests. To summarize, the technical objectives of the Base Program are: 1. Design pentamode acoustic cloaking materials, 2. Optimize these materials for cloaking applications, 3. Fabricate and test these materials in-air, to verify the mechanical properties, 4. Predict the cloaking behavior of the prototype materials in an in-water test. Successful prototype material fabrication and pre-test predictions will allow a determination of whether to proceed with the Option: 5. Execute an in-water test of acoustic cloaking using pentamode materials, 6. Process and analyze the test results.