Carbon nanotubes (CNTs) have record high tensile strength and Young’s modulus, which makes them ideal for making super strong yarns, ropes, fillers for composites, solid lubricants, etc. The mechanical properties of CNT bundles have been addressed in a number of experimental and theoretical studies. The development of efficient computational methods for solving this problem is an important step in the design of new CNT-based materials. In the present study, an atomistic chain model is proposed to analyze the mechanical response of CNT bundles under plane strain conditions. The model takes into account the tensile and bending rigidity of the CNT wall, as well as the van der Waals interactions between walls. Due to the discrete character of the model, it is able to describe large curvature of the CNT wall and the fracture of the walls at very high pressures, where both of these problems are difficult to address in frame of continuum mechanics models. As an example, equilibrium structures of CNT crystal under biaxial, strain controlled loading are obtained and their thermal stability is analyzed. The obtained results agree well with previously reported data. In addition, a new equilibrium structure with four SNTs in a translational cell is reported. The model offered here can be applied with great efficiency to the analysis of the mechanical properties of CNT bundles composed of single-walled or multi-walled CNTs under plane strain conditions due to considerable reduction in the number of degrees of freedom.

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.

This research paper studies the fracture and mechanical properties of rippled graphene containing dislocation dipoles. The atomistic simulation is performed to study the deformation behavior of pristine and defective wrinkled graphene. Graphene wrinkling considerably decreases the ultimate tensile strength of graphene with and without defects but increases the fracture strain. For graphene with the dislocation dipoles, temperature increase slightly affects mechanical properties, in contrast to graphene and graphene with Stone–Wales defect. The extremely similar slopes of the stress-strain curves for graphene with the dislocation dipoles with different arms imply that the distance between dislocations in the dipole does not have noticeable effects on the elastic modulus and strength of graphene. Defects in graphene can also affect its wrinkling; for example, preventing wrinkle formation.

The fullerene family, whose most popular members are the spherical C${}_{60}$ and C${}_{70}$ molecules, has recently added a new member, the cube-shaped carbon molecule C${}_8$ called a cubene. A molecular crystal based on fullerenes is called fullerite. In this work, based on relaxational molecular dynamics, two fullerites based on cubenes are described for the first time, one of which belongs to the cubic system, and the other to the triclinic system. Potential energy per atom, elastic constants, and mechanical stress components are calculated as functions of lattice strain. It has been established that the cubic cubene crystal is metastable, while the triclinic crystal is presumably the crystalline phase in the ground state (the potential energies per atom for these two structures are −0.0452 and −0.0480 eV, respectively).The cubic phase has a lower density than the monoclinic one (volumes per cubene are 101 and 97.7 Å${}^3$). The elastic constants for the monoclinic phase are approximately 4% higher than those for the cubic phase. The presented results are the first step in studying the physical and mechanical properties of C${}_8$ fullerite, which may have potential for hydrogen storage and other applications. In the future, the influence of temperature on the properties of cubenes will be analyzed.

Recent successes of researchers in the fabrication of new carbon structures of different morphologies and dimensions open up broad prospects for the development of carbon materials with qualitatively new properties. Such promising materials are cellular structures (or carbon aerogels) that have high deformability, good adsorption and conductivity characteristics. In this work, we consider a carbon structure consisting of re-entrant honeycomb cells, which allow the structure to be auxetic. The stability and deformation behaviour of re-entrant carbon honeycomb structures is studied by molecular dynamics simulation. The effect of structural parameters on the stability of carbon aerogel is discussed. It is shown that structural changes significantly depend on the strain rate and the loading direction. At a high strain rate in tension along the z-axis, all cells open slightly at the same time. On the contrary, at small strain rates, certain cells open, while others almost completely collapse, which is expected to result in changes in physical properties, for example, in conductivity. During tension along the x-axis, a transformation from a re-entrant honeycomb to a traditional honeycomb took place.

Molecular dynamics simulation is used to study the structures of fullerite of various composition as well as their mechanical properties. Fullerites based on fullerene C₆₀ with simple cubic and face-centered packing, fullerene-like molecule C₄₈ and fullerene C₂₄₀ with simple cubic packing are studied. Compliance and stiffness coefficients are calculated for fullerites C₆₀ and C₄₈. For fullerite C₂₄₀, C₆₀, and C₄₈, deformation behavior under the effect of hydrostatic compression is also investigated. It is shown that the fullerenes in the fullerite remain almost spherical up to high values of compressive strain, as a result of which the fullerite is an elastic medium up to densities of 2.5 g/cm³. The increasing stiffness and strength under an applied compression is found for all the considered fullerites.