International Journal of Computational Materials Science and Engineering

This paper investigates the postbuckling response of simply supported functionally graded beams under axial loading using several beam theories; classical beam theory, CBT, Timoshenko beam theory, TBT and parabolic shear deformation beam theory, PSDBT. Hamilton’s principle is used to derive the governing equations which are solved by closed-form method. It is assumed that the Young’s modulus is varying continuously in the thickness direction according to power-law form while all other material properties are taken to be constant. The effects of the reinforcement distribution, the beam edge-to-thickness ratio and the phase contrast (ratio of the reinforcement Young’s modulus to the matrix Young’s modulus) on the postbuckling behavior and critical buckling load of functionally graded beam are studied. Results demonstrate the important contribution of the shear effect to both the buckling and postbuckling behaviors. Finally, the combinations of reinforcement distribution, beam edge-to-thickness ratio and phase contrast that correspond to the highest and the lowest buckling capacities are identified.

Based on continuum mechanics and finite element method, a lamination model was developed for shape memory polymer composites (SMPCs) reinforced by woven fabrics. SMPCs were modeled as a laminated structure with woven fabric reinforcements embedded in shape memory polymers (SMPs). Thermo-responsive SMPs were defined by a 3D phenomenological model based on the phase transition approach, while woven fabric reinforcements were characterized by an anisotropic hyperelastic model. The proposed model was validated by comparing numerical results of a SMPC in the shape memory cycle of bending deformation with experimental data. Applications of the lamination model were demonstrated on numerical simulations of a tube made of SMPC in three shape memory cycles with different deformation modes. The proposed model is simple and applicable in the simulations of various shape memory cycles related to SMPCs. It also provides a theoretical foundation for the analysis and design optimization of woven fabric reinforced SMPC structures.

Slip or debonding of bonding interface is the key cause of the performance degradation or failure of the reinforced concrete (RC) member. In this paper, based on Monte Carlo method, a mesoscopic finite element model composed of mortar, coarse aggregate and steel rebar was established to consider the mesoscopic damage on the bonding interface and its influence on macroscopic performance deterioration of RC specimen. The results show that the simulation results fit well with experimental data. Higher initial interfacial damage results in lower bonding strength and smaller final displacement. Higher mortar modulus could greatly improve the initial bonding property and bonding strength, but slightly increase the final damage. Compared with the RC specimen model with plain steel bar, the model with deformed steel bar shows a longer duration of nonlinear increase for drawing force and lower bonding strength. When confinement is applied, the coalescence of damage zones is prevented due to the effect of thread. Therefore, the application of confinement could increase the bonding strength and the initial bonding property.

This paper deals with the theoretical calculation of structural and electronic, properties of AgBr and AgCl compounds using density functional theory within generalized-gradient (GGA) approximation and local density approximation (LDA). We employ the full potential linear muffin-tin orbitals (FP-LMTO) as implemented in the Lmtart code. We have used to examine structure parameter in eight different structures such as in NaCl (B1), CsCl (B2), ZB (B3), NiAs (B8), PbO (B10), Wurtzite (B4), HCP (A3) $\beta$Sn (A5) structures. The equilibrium lattice parameter, bulk modulus and its pressure derivative were presented for all calculated phases. The calculated ground state properties are in good agreement with available experimental and theoretical results. A pressure induced structural phase transition from NaCl (B1) to HCP (A3) phases at 37.66 and 18.11GPa for AgBr and AgCl, respectively, and from NaCl to CsCl phase in AgBr and AgCl at 90.55 and 24.4GPa, respectively, is also predicted. Furthermore, the band structures are computed. Our results are compared to other theoretical and experimental works, and excellent agreement is obtained.

The effect of Vanadium (V) doping on electronic and optical properties of NiO is discussed. Electronic and optical properties of a 32-atom supercell of V${}_x$Ni${}_{1-x}$O $(x=0.0625)$ obtained from first-principles calculations, performed within density functional theory (DFT), using the generalized gradient approximation (GGA) with the Hubbard potential $U$ were studied and compared to those of a 32-atom supercell of pure NiO. From the electronic structure and complex dielectric function analysis, the V doping causes the reduction of the bandgap by inducing the localized V $t_{2g}$ state in the NiO bandgap region, and the first optical transition for V-doped NiO occurs at a lower frequency than the one for the intrinsic NiO. The bandgap shrinkage to about 2 eV makes NiO when doped with V a potential candidate for visible light range application in photocatalytic applications. The resulting effects on refractive index, reflectivity, absorption, optical conductivity and loss function for V-doped NiO are compared to those of pristine NiO.

Density functional theory (DFT) within Wien2k code is utilized to compute the mechanical, thermal, electronic, magnetic and thermoelectric properties of the cubic spinel CoV₂O₄. The ground state lattice constant of CoV₂O₄ alloy agrees with previous literature. The calculated elastic constants of CoV₂O₄ predict that the present alloy is anisotropic, elastically stable and brittle. Beneficial acoustical applications are expected for the present alloy due to its high calculated Debye temperature and average sound velocities values. The longitudinal and transverse sound velocities modes of vibrations are found maximum along [110] directions compared to [100] and [111] directions. The calculated DOS and band structure show that CoV₂O₄ is electronically stable. The present alloy possesses a total magnetic moment of 12.0 ${\mu }_{\mathrm{\text{B}}}$ and is classified as a half-metallic ferromagnet. CoV₂O₄ shows $n$-type behavior and favors holes as charge carriers. The present alloy owns beneficial thermoelectric properties and can be used in thermoelectric applications.