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Abstract:
A comprehensive finite element-meshfree multiscale numerical framework is developed to investigate the size-dependent nonlinear asymmetric instability behavior of carbon nanofiber (CNF)-silicon carbide (SiC) nano-particle hybrid reinforced micro-arches subjected to radial concentrated loads applied at different positions. At the nanoscale, a finite-element-based homogenization strategy employing 3D periodic representative volume elements (RVEs) is developed to compute the effective elastic properties of nanocomposites reinforced with SiC nanoparticles and cylindrical CNFs, accounting for interphase characteristics. These homogenized material constants are subsequently incorporated into a nonlocal strain gradient theory (NSGT)-based radial point interpolation meshfree formulation, enhanced with an adaptive background decomposition integration approach to capture load location-sensitive nonlinear stability responses accurately. Numerical results demonstrate a pronounced multiscale coupling effect: increasing the CNF volume fraction from 1% to 4% results in approxi-
mately a 52% enhancement in all critical limit point loads, while increasing the SiC nanoparticle content from 1% to 5% increases them by nearly 29%. The relative interphase thickness provides a moderate gain of approximately 4.8%, and increasing the CNF aspect ratio strengthens the instability resistance by about 12.8%.
Conversely, increasing the SiC nanoparticle diameter results in a nearly 10.9% reduction in load-carrying capacity, indicating the superior reinforcing efficiency of smaller nanoparticles at a fixed volume fraction. Overall, the proposed framework successfully captures the highly nonlinear, curvature-sensitive, and size-dependent
instability characteristics of hybrid CNF-SiC micro-arches, offering a powerful predictive tool for the optimal design of advanced micro-scale structural components

Keywords:
Nonlinear stability, Meshfree approach, Size dependency, Finite element method, Hybrid composites

Abstract:
In the present exploration, by unifying the simplified unit cell (SUC) micromechanical approach with the isogeometric numerical technique, a new solution model is developed to examine the small-scale dependent nonlinear stability feature of fuzzy fiber reinforced composite (FFRC) microplates under in-plane axial compression. A notable structural feature of this hybrid composite is the presence of uniformly aligned radially grown carbon nanotubes (CNTs) on the surfaces of the glass fibers, all of equal length, together with the interphase area between the nanotubes and the polymer material. Additionally, the interphase region between CNTs and the matrix is modeled as a distinct phase. To capture the influence of material microstructure, the effective elastic constants are first predicted using the SUC micromechanics model, while size-dependent effects are incorporated through the modified strain gradient theory. These material characteristics are then combined with an isogeometric plate formulation to enable accurate and efficient numerical analysis of FFRC microplates with different geometries and boundary conditions. The results show that the presence of CNTs as well as the interphase region significantly enhances both the buckling resistance and postbuckling stability through improving the stiffness and load transfer capability, particularly when the interphase becomes thicker or stiffer. The examination also highlights the influence of glass fiber volume fraction as well as the role of strain gradient tensors in enhancing the load-bearing capability. Overall, the proposed framework provides a consistent link between micromechanical design features and structural-scale stability performance of FFRC microstructures.

Keywords:
Micromechanical model, Fuzzy fiber-reinforced composite, Size dependency, Interphase region

Abstract:
18-6-Graphdiyne (18-6-GDY) and C18N6 are low-density carbon-based nanomaterials with notable mechanical adaptability. Using molecular dynamics simulations, this study examines how random hydrogen functionalization affects their anisotropic mechanical behavior under uniaxial tension. Increasing hydrogen coverage from 2.5 % to 10 % degrades mechanical performance in both materials. The X-direction tensile strength of 18-6-GDY decreases from 28.8 to 19.0 GPa, while C18N6 shows a more pronounced reduction. Direction-dependent declines in Young's modulus and toughness highlight the combined influence of nitrogen substitution, hydrogen coverage, and lattice orientation.

Keywords:
Graphdiyne, N-Graphdiyne, Hydrogen functionalization, Molecular dynamics simulation

Abstract:
After the synthetization of graphene, various carbon allotropes with remarkable applications have emerged in
the material science. Net Y, closely related to Net C, is a novel carbon allotrope with exceptional properties. This study employs the molecular dynamics simulation to predict key mechanical characters of Net Y subjected to a uniaxial tension, including the failure strain as well as stress, Young’s modulus, and strain energy. A detailed tension distribution analysis is provided to explore its mechanical behavior further. The numerical results reveal that the defect density and temperature gradients significantly influence the mechanical performance of Net Y.
The nanosheet exhibits over twice the failure stress and 1.5 times the failure strain along with the X direction
than the initial failure stress and strain observed along with the Y direction. Also, it is demonstrated that the ultimate failure stress as well as strain along with the Y direction are more significant due to a substantial failure region in the associated stress–strain path. Furthermore, it is observed that the Young’s modulus declines consistently allocated to a higher defect density, decreasing by approximately 17 % via increasing the defect density from 0.5 % to 2 % along with the X direction. Moreover, the quantity of strain energy increases with the number of ribbons, reaching 1.58 × 10^(-26) eV and 3.99 × 10^(-26) eV along with the X and Y directions, respectively. The study also emphasizes the importance of defect location and structural stability through the tension distribution analysis.

Keywords:
Carbon allotrope, Net Y, Molecular dynamics simulation, Mechanical properties

Abstract:
Triphenylene-based graphdiyne (TPG) and nitrogen-doped TPG (NTPG) are recently developed two-dimensional nanomaterials with promising mechanical and electronic potential. The current study presents the first exploration of the hydrogen-functionalized TPG and NTPG nanosheets subjected to a uniaxial tensile loading condition using molecular dynamics simulations. The developed computational approach introduces a novel random functionalization scheme to improve the attributed structural stability. The Tersoff potential is employed to model the intra-layer interactions within the TPG. On the other hand, the interactions at the site of functionalization are described by the Dreiding force field for C and H atoms, supplemented by the Lennard-Jones (LJ) potential. The minimization process is applied via the conjugate-gradient technique, and following that, the system undergoes a canonical ensemble (NVT) simulation at 300 K with a timestep of 0.001 ps. In this step, the Nose–Hoover thermostat algorithm controlled the fluctuation of thermodynamic parameters, and the structure
surpassed a stable status. The achieved numerical results demonstrate that hydrogen coverage significant influences on the mechanical behavior, including failure stress and strain, Young’s modulus and toughness of TPG as well as NTPG nanosheets. For the both of nanosheets, increasing the hydrogen functionalization from
2.5 % to 10 % results in a consistent decline in mechanical properties. In the X direction, TPG shows a reduction
in ultimate stress from 15.08 GPa to 9.47 GPa, while NTPG drops more sharply from 30.87 GPa to 18.38 GPa. A similar trend is observed across the Y direction, with TPG decreasing from 11.42 GPa to 9.29 GPa, and NTPG from 30.35 GPa to 22.69 GPa.

Keywords:
Triphenylene graphdiyne, Nitrogen-doped TPG, Hydrogen functionalization, Molecular dynamics simulation, Mechanical properties,