Yingjing Liang

Molecular dynamics simulations were conducted to examine the effects of tensile, compressive, and torsional strains on thermal transport in boron nitride nanotubes (BNNTs) and boron nitride nanoribbons (BNNRs). Axial strain was found to reduce the thermal conductivity of both BNNTs and BNNRs, while torsional deformation further weakened heat transport in BNNTs, particularly in zigzag BNNTs. Quantitative analysis of the phonon density of states indicates that the reduction in thermal conductivity is associated with strain-induced redistribution of phonon spectra and intensified phonon scattering. Simulations with different BNNT chiralities further show that the thermal conductivity of BNNTs depends on chirality and the corresponding tube diameter, whereas the size-effect analysis of BNNRs reveals a clear dependence on ribbon length. These results provide a mechanistic basis for understanding strain-regulated phonon transport in boron nitride nanomaterials and suggest that strain engineering is a feasible strategy for nanoscale thermal-management applications.

Three-dimensional graphene metamaterials based on triply periodic minimal surfaces (TPMS) can achieve exceptional mechanical properties; however, the P-type Schwarz Primitive surface remains largely underexplored. For the first time, we quantified how unit cell size (30 Å, 45 Å, 60 Å), architectural dimensionality (0D, 1D, 2D), and tensile strain rate govern the uniaxial strength and fracture strain of pure carbon P-type multidimensional structures. Reactive molecular dynamics simulations reveal that both strength and fracture strain increase significantly as the unit cell size decreases. Furthermore, these structures exhibit distinct mechanical responses depending on their dimensionality, demonstrating a pronounced size effect. Additionally, strain rate plays a critical role: moderate strain rates facilitate atomic rearrangement and the formation of truss-like load-bearing networks, thereby enhancing load-bearing capacity. These findings establish clear structure-property relationships for scalable, ultralight carbon nano-architectures. All atomistic tensile tests were performed with LAMMPS using the AIREBO potential to describe C-C interactions. P-type Schwarz Primitive surfaces were generated with an in-house protocol that hexagonalizes a Delaunay triangulation without Voronoi tessellation. After energy minimization and 50 ps NVT equilibration at 300 K with a Nosé-Hoover thermostat, uniaxial tension was applied in strain-control mode while the lateral cell faces remained traction-free. Stress-strain curves and atomic fracture sequences were analyzed with OVITO.

Porous triply periodic minimal surface (TPMS) structures exhibit great potential for impact resistance applications. However, this research faces two main challenges. First, the design flexibility of single-sheet TPMS structures is limited, primarily affecting the core pore regions. Second, the influence of material properties on performance optimization has not been fully explored. This study introduces a hierarchical hybrid-embedding approach for two-sheet TPMS structures, embedding IWP substructures with customized relative densities into both the sandwich and core pores of a two-sheet P surface. We analyze the effects of material properties, specifically photosensitive resin, 316L stainless steel, and aluminum alloy, on structural performance. Experimental results reveal a clear correlation between material characteristics and energy absorption mechanisms. The two-sheet embedded TPMS structures made from brittle materials, such as photosensitive resin and aluminum alloy, show significantly improved energy dissipation through fracture-induced deformation. Specifically, photosensitive resin exhibits a 700% increase in yield stress and a 1326% improvement in energy absorption, while aluminum alloy shows a 28.4% and 87.9% improvement, respectively. In contrast, 316L stainless steel, which relies on plastic deformation for energy dissipation, shows only modest improvements of 13.4% in yield stress and 3.2% in energy absorption. These findings not only demonstrate the enhanced impact resistance of the two-sheet embedded TPMS design but also highlight the critical role of material properties in optimizing topological structures. This research provides valuable insights for impact-resistant structural design, with practical applications in aerospace, civil infrastructure, and advanced manufacturing.

Two-dimensional materials have now become the main components of nanoelectromechanical systems due to their outstanding properties in practical application. This study investigates dynamic friction between rotational graphene layers under equi-biaxial tensile and shear strain via molecular dynamics simulations from the perspective of energy dissipation. To eliminate the influence of commensurability and the edge effect, a friction pair model with annular graphene as a slider is established. The mechanisms of strain effect coupling with temperature, rotational frequency, and supporting stiffness on the interlayer friction are analyzed. The results indicate that tensile strain reduces interlayer friction, while the shear strain effect on friction varies with temperature. The mechanism of frictional dissipation is explained from the perspectives of interface moiré pattern, entropic effect, interatomic interactions, effective contact atoms, in-plane deformation, out-of-plane lattice vibration, and phonon state density. The results of the research will provide a theoretical basis for the design and manipulation of nanoelectromechanical systems and two-dimensional materials.

This study delves into the mechanism of dynamic sliding friction between layers of graphene and its strain effect, through numerical analysis using molecular dynamics simulations. To eliminate the influence of commensurability and edge effect, a friction pair model with annular graphene as a slider is established. The research explores the quantifying effects of temperature, normal load, sliding velocity, support stiffness, and axial strain on the friction between graphene layers. The coupling effect of temperature and other influencing factors is also clarified. The results indicate that the interlayer friction increases with normal load by decreasing the interlayer spacing and increasing the atomic vibration amplitude. The ploughing phenomenon does not appear since the edge effect is eliminated by the model. Friction is initially enhanced at higher sliding velocities, but is later reduced by severe residual deformation and lattice resonance frequency. The support stiffness regulates interlayer friction by affecting the atomic vibration amplitude of the graphene lattice. Mechanism analysis shows that the number of effective contact atoms increases under axial strain, and the lattice vibration frequency is the main way to regulate the interlayer friction by strain effect. Our findings provide a fundamental understanding of the strains engineering of nanoscale friction and reveal the influence mechanism of affecting factors on the dynamic friction of graphene.

Negative Poisson’s ratio (auxetic) material is one of the most widely studied metamaterials, and recent attempts have been made to discover auxeticity in graphene-based and related carbon-based materials. However, it is shown that negative Poisson’s ratio effect requires special conditions, such as high temperature. Achieving negative Poisson’s ratio effect under large strain at ambient conditions is the key to graphene materials in nano-device applications. In order to discover the auxetic properties of nanostructures under large strain, this article proposes periodically rotating graphene nanostructures (PRGNs) which are the combination of graphene and rotating rigid unit structures. Poisson’s ratio, Young’s modulus, and damage mechanism of PRGNs are investigated using molecular dynamics simulation. It can be possible to conclude that PRGNs can also exhibit auxetic behavior, and their negative Poisson’s ratio effect can be maintained even at large strains ( ε ∼ 0.1). Poisson’s ratio can be regulated by adjusting the value of the geometry parameters of the graphene sheets (GSs), which comprise the PRGNs, and changed from negative to positive and from positive to negative. Also, the influences of the structural size of GSs and the connection angle between GSs on the mechanical properties are explored, which will provide a theoretical basis for the preparation and performance optimization of GSs and the nano-auxetic properties of materials.

Although highly desirable, the experimental technology of the dynamic mechanical properties of materials under multiaxial impact loading is rarely explored. In this study, a true-biaxial split Hopkinson pressure bar device is developed to achieve the biaxial synchronous impact loading of a specimen. A symmetrical wedge-shaped, dual-wave bar is designed to decompose a single stress wave into two independent and symmetric stress waves that eventually form an orthogonal system and load the specimen synchronously. Furthermore, a combination of ground gaskets and lubricant is employed to eliminate the shear stress wave and separate the coupling of the shear and axial stress waves propagating in bars. Some confirmatory and applied tests are carried out, and the results show not only the feasibility of this modified device but also the dynamic mechanical characteristics of specimens under biaxial impact loading. This novel technique is readily implementable and also has good application potential in material mechanics testing.

This paper investigates the deformation mechanism and energy absorption behaviour of 316 L triply periodic minimal surface (TPMS) structures with uniform and graded wall thicknesses fabricated by the selective laser melting technique. The uniform P-surface TPMS structure presents a single-level stress plateau for energy absorption and a localized diagonal shear cell failure. A graded strategy was employed to break such localized geometrical deformation to improve the overall energy absorption and to provide a double-level function. Two segments with different wall thicknesses separated by a barrier layer were designed along the compression direction while keeping the same relative density as the uniform structure. The results show that the crushing of the cells of the graded P-surface TPMS structure occurs first within the thin segment and then propagates to the thick segment. The stress–strain response shows apparent double stress plateaus. The stress level and length of each plateau can be adjusted by changing the wall thickness and position of the barrier layer between the two segments. The total energy absorption of the gradient TPMS structure was also found slightly higher than that of the uniform TPMS counterparts. The gradient design of TPMS structures may find applications where the energy absorption requires a double-level feature or a warning function.

We investigate the propagation behavior of the low-frequency topological interface state of the flexural wave in the locally resonant metastructure and analyze the tunability of the sub-wavelength interface states by the piezoelectric shunting circuit. One homogeneous thin beam is periodically attached with local resonant beams, which connect shunted piezoelectric actuators. The folding band obtained by merging two primitive unit cells into one new element can generate a Dirac point below the low-frequency locally resonant bandgap. This folding point is opened to develop one new bandgap originated from the Bragg scattering effect by breaking the mirror symmetry. Then, topological transitions are demonstrated during the distance variation between two adjacent resonances. The interface state’s existence is further confirmed by using steady and transient analysis of the heterostructure composed of two media with different topological properties. Finally, we show the relationship between the interface frequency and the capacitance ratio and research the influence of the distance parameter on the topological interface state. Because of the tunability of elastic waves by the piezoelectric shunting circuit, our design has potential for applications such as energy harvesters, filters, and physical switches.