Harnessing local flow in buckling pores for low-frequency attenuation

Abstract

While attenuation at low frequencies remains highly desirable for industrial applications such as multistory buildings or spacecraft propellant tanks, fluid-filled rocks can achieve this goal naturally by so-called local flow in their heterogeneous pore structure. The present work aims at combining this natural phenomenon with controlled instabilities in light-weight structures. Buckling of their pores is harnessed to break local geometric symmetry and maximize the local-flow effect. A prototype structure with elliptical pores is analyzed numerically. It does not show local flow or attenuation for the starting geometry, but reversibly switches into an attenuating structure by imposing a critical buckling strain. The simulations reach inverse quality factors larger than 0.3 around 5Hz for material properties of air-filled silicone rubber. A key to high attenuation is a tradeoff between the unstable structure and the pore fluid. If the solid is too soft, the fluid-filled pores are not compressed and buckling is not triggered. If the solid is too stiff, most energy is stored elastically and not dissipated by fluid flow. The proposed, fluid-filled structure allows for a scalable, light-weight material exhibiting significant low-frequency attenuation.