Large-scale underwater acoustic cloak based on honeycomb lattice pentamode metamaterials.

This research explores the development and modeling of an underwater acoustic cloak utilizing pentamode metamaterials. The primary objective is to design a structure that acoustically mimics water, enabling the guidance of waves in such a way that the target object is acoustically cloaked. Initially, an aluminum-based frame arranged in a honeycomb lattice is designed, and its phononic band structure is analyzed. Elliptical-shaped masses are then embedded into the structure to tune its mechanical properties for optimal acoustic performance. Finite element method simulations demonstrate that the designed structure exhibits good agreement with wave propagation in water. Subsequently, the acoustic cloak is designed using graded variations in structural parameters, and its performance is evaluated within the frequency range of 1 to 3 kHz. The results show that the proposed structure can effectively reduce the total scattering cross section by a factor of two and successfully cloak an object with an approximate area of 34,880 mm².