Researches in Acoustic Black Hole (ABH) structures are attractive for potential applications in broadband vibration suppression and wave manipulation. The remarkable functions of an ABH element are limited below the cut-on frequency, above which the broadened ABH effect can be effectively obtained. The mid-to-low application challenges the ABH structure without large dimensions. In this work, the band structures of two-dimensional (2D) ABH lattice structure without additional damping material were investigated to get insight into the potential bandgap property induced by 2D ABHs. The simulation results show that periodic 2D ABHs can achieve flexural wave bandgaps (BGs) below the cut-on frequency of ABH cell. The analysis results of eigenmodes show that the generation of multiple BGs is dominated by the ABH-induced local resonance at multiple frequencies. The effect of lattice constant and key parameters of the ABH on the BGs is also explored to indicate the bandgap adjustment rules, while examining the vibration attenuation in fixed-size plates with finite periodic cells. The results show a trend of shifted and partially overlapping BG for different parameters. Larger lattice constant results in the disappearance of bandgaps due to the eigenstate transition and ABH cell with smaller size achieves the first bandgap in higher frequency. The bandgap investigation as well as the strategies for bandgap adjustment enrich the existing knowledge on periodic 2D ABH structures and offer a design guideline of bandgap behaviors in a 2D ABH plate strip.

Flexural wave bandgap; 2D Acoustic black hole; multiple frequency; vibration attenuation