International Journal of Computational Materials Science and Engineering

In this paper, new tangent shape function-based higher-order transverse shear deformation theory (NTHSDT) is proposed to compute the buckling behavior of the elastically supported functionally graded material (FGM) sandwich plates under porous medium. The proposed theory is found to be variationally consistent and fulfills the zero traction boundary conditions on the bottom and top layer without a shear correction factor. The material properties are presumed to be graded in the thickness direction as characterized by a modified power law distribution in terms of volume fraction of constituents. The governing equations are derived using Hamilton’s Principle. A strong form of solution discretizes the governing equations by employing a thin plate spline radial basis function-based collocation (TSRBFC) method. The proposed theory is efficient, reliable, and is in close agreement with the results in the literature. Comparison studies show that the NTHSDT is more accurate than other plate theories and is simple in analyzing buckling behavior. A parametric study is done to examine the effects of grading index, porosity index, sandwich schemes, aspect ratio, side-to-length thickness ratio and foundation stiffness.

In recent years, use of chitosan (CS) nanoparticles as nanocarriers received much attention due to their bio-degradability, biocompatibility and non-toxicity. Water-soluble sulfated CS derivatives are widely used as anticoagulant and antiviral drugs. The chitosan sulfates (CSS) containing one-to-three sulfate groups were investigated using 0the DTF. The energy gap $(\mathrm{\Delta }E)$, electronegativity ($\chi$), electron affinity (EA), chemical potential $(\mu )$, ionization potential (IP), hardness $(\eta )$, softness $(\varsigma )$, electrophilicity index $(\omega )$, and maximum charge transfer index $(N_{max})$ were obtained by the B3LYP/6-31++G(d,p) method. The electronic and thermodynamic properties, Mulliken atomic charges of sulfated chitosan with different contents of sulfate groups were obtained using the B3LYP/6-31++G(d,p) method.

Polymer-derived ceramics (PDCs) which are fabricated through pyrolysis of preceramic polymers have attracted increasing attention due to their versatility in structure architecture design and property tailoring. Shaping at the polymer state using 3D printing allows the final ceramic products to exhibit arbitrary shapes and complex architectures that are otherwise impossible to achieve through traditional processing routes. The polymer-to-ceramic phase transition also provides additional space for mechanical property tailoring. A multiscale computational model is developed to explore the phase transition mechanisms and their correlations with processing parameters and failure response. Calculations in this work concern PMHS/DVB preceramic polymers. Molecular dynamics (MD) simulations are carried out first to track the atomic structure evolution at different temperatures. Continuum-scale ceramic phase formation is calculated on the basis of the competition between gas generation and gas diffusion. The effect of processing parameters on mechanical properties of pyrolyzed PMHS/DVB is systematically studied. Conclusions from this study can provide direct guidance for fabricating PDC composites with tailored mechanical properties.

Metal matrix-based carbon nanotube (CNT) composites are being extensively explored because of their superior mechanical properties. Among metals, magnesium due to its low density and low melting point is widely used in making light weight composite material. Addition of small amount CNTs in magnesium matrix can produce high strength, light weight material. In this work, mechanical properties of CNT/Magnesium composites are being investigated. Three-dimensional representative volume element is extracted from the composite, for the analysis. Four different types of models are constructed, each made of square shape consisting of 16 CNTs. Adequate properties of single-walled CNT/Magnesium composite are examined with RVE undergoing stretch and transverse loading conditions. The results are obtained for different percentages of CNT volume fraction in magnesium matrix. For closely simulating the properties of composite material, the interphase is developed between CNT and matrix material and random orientation of carbon nanotubes in the matrix is considered. With the insertion of 2.4% of CNTs in the magnesium matrix material, 31.64% rise in Young’s modulus is observed. The results acquired from the present analysis are validated with the rule of mixture results. The present results are observed to be in line with the experimental results from the literature.

Aluminum nanoparticle (ANP) in liquid Cellulose dinitrate decamer sol was investigated by ReaxFF molecular dynamics simulations. The mechanism of nitrocellulose (NC) single chain adsorption was researched as a chemisorption process. New Al–O bonds are formed by dehydrogenation and denitrification of the nitrate ester groups. The adsorbed part of the NC chain drags other parts to the surface as a horizontal adsorption state. We also simulated the processes of liquid Cellulose dinitrate decamer sol (ethanol, diethyl ether, and NC three components) coating the ANPs at different temperatures. The results indicate that the organic coating near surface is mainly consisted of ethanol and diethyl ether molecules. The NC chains are adsorbed on the ANPs surface in two states, including the horizontal adsorption or the nearly vertical adsorption. Heating can increase the coating rate without significantly changing the composition of the coating. Finally, the oxidation simulation shows that the organic layer can maintain good stability and oxidation resistance.

We have explored the interaction of Ni/Cr with pyridinic N-doped graphene and its influence on the electronic and magnetic characteristics of graphene using a density functional theory (DFT) approach. A $5\times 5$ graphene supercell with a single vacancy is modeled. Initially, the concentration of nitrogen atoms is varied in the pyridinic configuration of graphene. The structures, thus obtained, are decorated with Ni/Cr atoms. For configurations without transition metals (TMs), the calculated electronic band structures show a downward shift in Fermi level that decreases as nitrogen concentration increases. Furthermore, it is found that these structures manifest metallic behavior along with some flat bands near the Fermi level. With the addition of Ni/Cr atoms, the movement of the Fermi level toward the conduction band is noticed. The opening of the bandgap at the K-point also varies slightly with the concentration of N atoms and/or the presence of TM atoms. The structures P1N-Ni and P2N-Ni transmute into semiconductors. A significant increase in the magnetic moment is found with the adsorption of the Ni/Cr atom. The analysis of spin-polarized partial density of states proves that higher magnetic moments following TM absorption are mainly on account of the Ni/Cr-3d orbitals and their hybridization with C-2p orbitals. These findings suggest that functionalizing TMs on pyridinic N (Nitrogen)-doped graphene can drastically alter their electronic and magnetic properties.