Role of a fractal shape of the inclusions on acoustic attenuation in a nanocomposite

TL;DR

This study uses finite element simulations to show that dendritic, fractal-shaped inclusions in nanophononic materials significantly enhance acoustic attenuation due to increased phonon-interface scattering, especially at short wavelengths.

Contribution

It demonstrates how fractal-shaped inclusions influence acoustic attenuation in nanophononic materials, highlighting the role of dendritic geometries in phonon scattering.

Findings

Dendritic inclusions increase acoustic attenuation via phonon-interface scattering.

Strong attenuation observed when wavelength is much smaller than inter-inclusion distance.

Attenuation fits a compressed exponential function with β>1.

Abstract

Nanophononic materials are promising to control the transport of sound in the GHz range and heat in the THz range. Here we are interested in the influence of a dendritic shape of inclusion on acoustic attenuation. We investigate a Finite Element numerical simulation of the transient propagation of an acoustic wave-packet in 2D nanophononic materials with circular or dendritic inclusions periodically distributed in matrix. By measuring the penetration length, diffusivity, and instantaneous wave velocity, we find that the multi-branching tree-like form of dendrites provides a continuous source of phonon-interface scattering leading to an increasing acoustic attenuation. When the wavelength is far less than the inter-inclusion distance, we report a strong attenuation process in the dendritic case which can be fitted by a compressed exponential function with $\beta>1$.