Abstract: A gear-based mechanical metamaterial with continuously adjustable elastic parameters in a large range is provided. The gear-based mechanical metamaterial includes a gear array, a frame and connecting shafts. The gear array is formed by periodically extending mechanical metamaterial cells along an x direction and a y direction. Each of the mechanical metamaterial cells is formed by arranging a multiple gears. Adjacent gears of the multiple gears are meshed with each other. Each of the multiple gears includes a center hole and two centrosymmetric irregularly-shaped holes. A thickness of an elastic arm between the each of two centrosymmetric irregularly-shaped holes and an outer wall of a corresponding one of the multiple gears is uniformly increased or decreased. Each of the connecting shafts is arranged in a center hole of a corresponding one of the multiple gears.

Abstract: The present disclosure provides a thin-layer low-frequency underwater sound insulation metamaterial, including two cover plates and a sound insulation layer. The sound insulation layer is composed of sound insulation components arranged in an array periodically. The sound insulation components each include a sound insulation unit and four connecting units. The sound insulation unit is of a hollow rectangular column structure. The four connecting units are arranged at four corners of the sound insulation unit. Every two adjacent sound insulation units are connected through the connecting units. A long side wall of the sound insulation unit and the corresponding cover plate have an included angle of 0-90°. The metamaterial can obtain a smaller equivalent acoustic impedance in propagation direction of acoustic waves, and compared with a sound insulation material of a square honeycomb structure with the same thickness, the metamaterial has greatly improved sound insulation performance.

Abstract: A gear-based mechanical metamaterial with continuously adjustable elastic parameters in a large range is provided. The gear-based mechanical metamaterial includes a gear array, a frame and connecting shafts. The gear array is formed by periodically extending mechanical metamaterial cells along an x direction and a y direction. Each of the mechanical metamaterial cells is formed by arranging a multiple gears. Adjacent gears of the multiple gears are meshed with each other. Each of the multiple gears includes a center hole and two centrosymmetric irregularly-shaped holes. A thickness of an elastic arm between the each of two centrosymmetric irregularly-shaped holes and an outer wall of a corresponding one of the multiple gears is uniformly increased or decreased. Each of the connecting shafts is arranged in a center hole of a corresponding one of the multiple gears.