Interactive behavior of internal resonators in acoustic metamaterials under impact pulse loading

Abstract

Acoustic metamaterials exhibit negative effective mass density when the lattice system consists of mass-in-mass microstructural units. It is found out that the effective mass density becomes frequency dependent and displays negativity for frequencies near the resonant frequency of the internal resonators. The effect of a negative mass property implies that stress wave propagation is prohibited; leading to structural applications like vibration control, impact protection and shock wave mitigation. Under impact loading, internal resonators are revealed to effectively reduce the displacement/velocity of the overall structure, and attenuate a specifically-designed range of frequency where the negative effective mass density is exhibited. However, researchers have yet to study the mutual interaction between the internal resonators. Knowing how adjacent resonators interact and response to dynamic profile of preceding resonators may lead to more efficient design for stress wave attenuation. In this paper, we performed detailed investigation on the interactive behavior of internal resonators in acoustic metamaterials under an impact pulse load. Finite element analysis results show that when internal resonators are adjacently placed, they produce a coupled resonance effect, resulting in a leakage of frequency just below the resonant frequency of the resonators. This frequency leakage can lead to energy storage and harvesting applications.