Development of Structures with 2D Materials for Applications in Mechanical Wave Shielding

Abstract

In this work, we have studied, through computational modeling and experimental verification, phononic band gaps in foam and three lattice structures (namely simple cubic, body centered cubic, and face centered cubic lattice). Phononic band gap in a structure refers to a frequency range of which no mechanical wave is allowed to propagate. The intuitive interpretation is that multiple scattering of mechanical wave induces destructive interference at the interfaces of different materials. For computational work, Bloch's theorem in electronic wave propagating in crystal lattice is employed to calculate the phononic band gap; and finite element method (FEM) is utilized to perform calculation. The mechanisms of the opening of band gap in the aforementioned structures were investigated. From computational modeling, the geometrical contrast in components constituting a lattice structure is found to be the key of the presence of phononic band gap. Difference geometries provide difference frequency groups and the frequency difference between two adjacent groups is the phononic band gap. In addition, second band gap may exist and it could be attributed to the frequency difference in the same frequency group. Transferring from simple cubic lattice to body centered cubic lattice and face centered cubic lattice could induce pass bands which make tunneling through the band gap. The more connection between difference geometries in a unit cell lead to narrowing of band gap. Besides numerical investigation. Experiments were carried out to study the mechanical transmission through different lattices. The setup was designed with a function generator, an oscilloscope and two piezo disks. A LabVIEW program was developed in house to control the system and process the data. Foam-like structures and 3D-printed lattices were studied. Mechanical compression and mechanical wave transmission were tested for each type of samples. It was shown from our results that no apparent phononic band gap exist in foam-like structure due to its random structure. The mechanical wave transmission through 3D-printed polymer lattice verifies the numerical calculation. Also, a dip-coating method based on ethanal solution was developed to coat two-dimensional (2D) materials, namely, graphene oxide and MXene, on polymer lattice which gives possibility to build a structure with dual shielding properties.

Date of Award	Jul 2021
Original language	American English