In this presentation, a lightweight metastructure is designed based on the prismatic tensegrity structure which enables uniquely coupled compressional and torsional waves. A prismatic tensegrity structure consists of elastic bars and cables with pre-stress to provide its stiffness and therefore, has very high strength-to-weight ratio. A theoretical model with coupled compressional-torsional stiffness matrix is developed to study the band structure of the proposed metastructure. Microstructure designs based on both Bragg scattering and local resonance mechanism are investigated for vibration isolations in different targeted frequency ranges. It is noticed that unit cell with opposite chirality can lead to broadband isolation for both compressional and torsional vibrations. Interesting wave mode mixing and selective wave mode transmission phenomena are also studied based on the proposed theoretical model. Moreover, tunable wave propagations and vibration suspension are achieved by two approaches: (i) harnessing the geometrically nonlinear deformation of the periodical tensegrity prisms under global torsional or/and compressional loads to achieve large-range and coarse adjustment of the band structure; (ii) modifying the pre-stress in the tension cables with active components, such as hydraulic actuators, for small-range and fine adjustment of the band structure. The proposed tensegrity metastructure could be useful for various engineering applications in the fields of space and civil engineering where high strength-to-weight ratio as well as broadband vibration suspension are in a high demand.
In this work, perfect elastic wave mode transmission and isolation in an anisotropic Pentamode Material (PM) slab sandwiched between two semi-infinite isotropic solids are first explored. Selective elastic wave mode filtering is achieved in a broad frequency range. Furthermore, elastic wave experiments are conducted, which are in good agreements with the full-wave finite element simulations. As a result, the anisotropic PM greatly expands the horizon of subwavelength elastic wave control with broadband advantage. Such filtering abilities can be very useful for underwater noise isolation and elastic wave manipulation devices.