Directional Wave Control Via Elastic Anisotropy in Mechanical Metamaterials

Abstract A design methodology is proposed for architected microstructures that exhibit highly anisotropic and tunable stiffness, achieved solely through geometric configuration without modification of the material composition. Systematic variation of key geometric parameters yields stiffness anisotropy exceeding three orders of magnitude, thereby enabling independent control of axial and shear moduli. Such decoupled stiffness tailoring provides substantial flexibility for optimizing mechanical performance across diverse engineering applications. The dynamic characteristics of the proposed microstructures are comprehensively investigated, revealing pronounced wave anisotropy, directional energy transmission, and frequency-dependent phenomena, including directional bandgaps, single-mode propagation, and wave mode conversion. In particular, mode conversion enables elastic waves to be redirected by 90 deg, while the adoption of an oblique lattice enhances conversion efficiency and broadens the directional bandgap, thereby improving waveguiding performance. The concept is further extended to an annular metastructure, which exhibits efficient wave trapping and azimuthal energy confinement, in sharp contrast to the omnidirectional propagation observed in isotropic counterparts. These findings establish a rigorous framework for the design of anisotropic architected materials with finely tunable wave control, offering significant potential for applications in vibration isolation, acoustic steering, and energy localization.