2025/05/08 by Philip A. Cotterill, Cotterill, Philip A, David Nigro +3
Engineering · Materials Science · #Acoustic Wave Phenomena Research #Applied Physics (physics.app-ph) #Cellular and Composite Structures #FOS: Physical sciences #Metamaterials and Metasurfaces Applications
paper · pdf · doi:10.48550/arxiv.2505.05344
openalex publication_date 2025/05/08 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Electromagnetic bi-anisotropy finds an analogy in acoustic metamaterial science as Willis coupling. Its impact and emergence in the field of elastodynamic metamaterials is not as well understood however, given the coupling between compressional and shear waves. Here we discuss the emergence of Willis coupling in heterogeneous elastic slabs embedded in an acoustic fluid. The microstructure of the slab comprises circular cylindrical voids and asymmetry is present via two neighbouring line arrays, each with a repeating void of differing radius. The slab matrix is soft, with Poisson ratio close to 1/2 so that the voids act as Giant Monopole Resonators, and induce a strong dynamic response at low frequency. The incorporation of Willis constitutive coupling ensures that a unique set of effective material properties can be assigned to the slab up to a maximum frequency defined by the periodic spacing of the voids and the elastic properties of the substrate. Including loss in the elastic medium via its shear modulus induces strong directional-dependent absorption at low frequency, whilst of course maintaining reciprocity.