Pentamode metamaterials with ultra-low-frequency single-mode band gap based on constituent materials

An effective method for realizing ultra-low-frequency single-mode band gap in pentamode metamaterials is proposed based on constituent materials. Results show that the decreasing ratioE/ρ(stiffness/mass density) of constituent material can significantly lower the frequency range of single-mode band gap. By merely replacing the constituent material from Al to rubber, the center frequencyf_cof single-mode band gap can be reduced nearly 600 times (from 3621 Hz to 6.5 Hz), while the normalized bandwidth Δf/f_cand the ratio of bulk modulusBto shear modulusGof pentamode structure keep substantially stable. The nonlinear fitting demonstrates that the relation betweenf_candE/ρsatisfies the logarithmic function. The two-component pentamode structure is designed to further explore the ultra-low-frequency single-mode band gap. The effects of thick-end diameterDof double-cone, diameterD₀and material type of additional sphere, on single-mode band gap of two-component system are analyzed. This work is attractive for several ∼Hz acoustic/elastic wave regulations using pentamode metamaterials.