Metamaterials for Acoustic Cloaking

The goal of this Phase II will be a full scale demonstration of an acoustic metamaterial cloak on a UUV-like vehicle. The design will be based on the Cummer-Schurig cylindrical solution for a perfect 2-D cloak surrounding a rigid cylindrical object. The first effort will be a theoretical task in conjunction with KSU to evaluate important issues related to the abstract nature of the Cummer-Schurig solution, which calls for infinite mass density and stiffness boundary conditions and purely real dynamic quantities (i.e., no losses). The type of resonant dynamical element to be used in the design to create the anisotropic mass densities required will be selected. Two major candidates identified in Phase I are resonant masses requiring voids encapsulated by high rigidity structures (e.g. shells) and a system of shaped inclusions embedded directly in an elastomer matrix. Laboratory experiments guided by co-evolving analytical and numerical models will be performed to demonstrate the required dynamical behavior for each treatment layer, to be followed by fabrication and testing larger cloak layer samples to assure that properties are maintained with scale up. Finally, a full scale demonstration will be conducted with a suitable vehicle or stand-in structure.