Close packed carbon nanotube bundles are materials with highly deformable elements, for which unusual deformation mechanisms are expected. Structural evolution of the zigzag carbon nanotube bundle subjected to biaxial lateral compression with the subsequent shear straining is studied under plane strain conditions using the chain model with a reduced number of degrees of freedom. Biaxial compression results in bending of carbon nanotubes walls and formation of the characteristic pattern, when nanotube cross-sections are inclined in the opposite directions alternatively in the parallel close-packed rows. Subsequent shearing up to a certain shear strain leads to an appearance of shear bands and vortex-like displacements. Stress components and potential energy as the functions of shear strain for different values of the biaxial volumetric strain are analyzed in detail. A new mechanism of carbon nanotube bundle shear deformation through cooperative, vortex-like displacements of nanotube cross sections is reported.

In the present work, the thermal conductivity and thermal expansion coefficients of a new morphology of Ni/graphene composites are studied by molecular dynamics. The matrix of the considered composite is crumpled graphene, which is composed of crumpled graphene flakes of 2–4 nm size connected by van der Waals force. Pores of the crumpled graphene matrix were filled with small Ni nanoparticles. Three composite structures with different sizes of Ni nanoparticles (or different Ni content—8, 16, and 24 at.% Ni) were considered. The thermal conductivity of Ni/graphene composite was associated with the formation of a crumpled graphene structure (with a high density of wrinkles) during the composite fabrication and with the formation of a contact boundary between the Ni and graphene network. It was found that, the greater the Ni content in the composite, the higher the thermal conductivity. For example, at 300 K, $\lambda$ = 40 W/(mK) for 8 at.% Ni, $\lambda$ = 50 W/(mK) for 16 at.% Ni, and $\lambda$ = 60 W/(mK) for 24 at.% Ni. However, it was shown that thermal conductivity slightly depends on the temperature in a range between 100 and 600 K. The increase in the thermal expansion coefficient from 5 × 10${}^{-6}$ K${}^{-1}$, with an increase in the Ni content, to 8 × 10${}^{-6}$ K${}^{-1}$ is explained by the fact that pure Ni has high thermal conductivity. The results obtained on thermal properties combined with the high mechanical properties of Ni/graphene composites allow us to predict its application for the fabrication of new flexible electronics, supercapacitors, and Li-ion batteries.

Interatomic interaction potentials are compared using a molecular dynamics modeling method to choose the simplest, but most effective, model to describe the interaction of copper nanoparticles and graphene flakes. Three potentials are considered: (1) the bond-order potential; (2) a hybrid embedded-atom-method and Morse potential; and (3) the Morse potential. The interaction is investigated for crumpled graphene filled with copper nanoparticles to determine the possibility of obtaining a composite and the mechanical properties of this material. It is observed that not all potentials can be applied to describe the graphene–copper interaction in such a system. The bond-order potential potential takes into account various characteristics of the bond (for example, the angle of rotation and bond lengths); its application increases the simulation time and results in a strong interconnection between a metal nanoparticle and a graphene flake. The hybrid embedded-atom-method/Morse potential and the Morse potential show different results and lower bonding between graphene and copper. All the potentials enable a composite structure to be obtained; however, the resulting mechanical properties, such as strength, are different.

Using numerical computer simulation, the behavior of disordered dislocation systems under the action of monochromatic standing sound wave has been investigated in the grain of the model two-dimensional polycrystal containing nonequilibrium grain boundaries. It has been found that the presence of grain boundaries markedly affects the behavior of dislocations. The relaxation process and changes in the level of internal stresses caused by the rearrangement of the dislocation structure due to the ultrasonic action have been studied.