Flexural Wave Attenuation in Sandwich Beams: Synergy of Discontinuous Sandwich Cores and Embedded Acoustic Black Holes

This study proposes a novel sandwich beam structure designed for superior low-frequency broadband flexural wave control. The proposed structure synergistically integrates discontinuous sandwich cores with Acoustic Black Holes (ABHs) embedded in the face sheets, demonstrating performance that outperforms conventional designs. To elucidate the coupling mechanisms between the periodic effects of discontinuous cores and ABH effects, two distinct configurations are systematically investigated: the C-ABH and NC-ABH sandwich beams. The sandwich beam with ABHs embedded in the beam segments coupled with the core is designated as C-ABH sandwich beam, while that with ABHs embedded in the segments non-coupled from the core is termed NC-ABH sandwich beam. A wave vector method is employed to establish flexural wave propagation models for both beam configurations, alongside a transmission coefficient model characterizing flexural wave attenuation. Using these models, the influence of four key factors is investigated on the flexural wave attenuation performance of the sandwich beams. Research results show that the proposed NC-ABH sandwich beam delivers superior flexural wave attenuation performance; the attenuation performance is markedly enhanced by embedding ABHs in the face sheet with higher flexural rigidity and by increasing the flexural rigidity asymmetry between the upper and lower face sheets; reducing the ABH minimum thickness and increasing its length and quantity further widen the bandgaps and shift them toward lower frequencies. These findings indicate that the proposed NC-ABH sandwich beam offers an effective strategy for achieving strong flexural wave attenuation in low-frequency broadband applications.