Dynamic Behavior of Metacomposites

Abstract

Acoustic/Elastic/Mechanical (AEM) metamaterials exhibit negative effective mass density when the lattice system consists of mass-in-mass microstructural units. AEM metamateirals fall within the family of composites, since the constituents are the microstructural units embedded within the composite matrix. It is found out that the effective mass density of AEM metacomposite becomes frequency dependent and displays negativity for frequencies near the resonant frequency of the internal resonators. The effect of a negative mass property simply implies that stress wave propagation is prohibited; this leads to structural applications like vibration control, impact protection and shock wave mitigation. Under impact loading, internal resonators in the AEM metacomposite are revealed to effectively reduce the displacement and velocity of the overall structure, and attenuate the stress wave propagation over a specifically-designed range of frequency where the negative effective mass density is exhibited. In this paper, the transient and dynamic behavior of AEM metacomposites is analyzed. Firstly, the concept of AEM metamaterials is introduced by presenting the unique property of negative effective mass density through simple analytical mass-in-mass models. Next, the impact wave attenuation capability of the metacomposites is demonstrated using computational simulation. In particular, this study investigates the mechanical energy incurred by the internal resonators of an AEM metacomposite when the structure is subjected to an impact pulse load. Both strain energy and kinetic energy, as well as the total mechanical energy are considered. Results revealed that the mechanical energy consideration agrees well with the kinematic characteristics of the resonators in the system.