International Journal of Computational Materials Science and Engineering

In this research, a size-dependent Euler–Bernoulli beam model is proposed for nonlinear free vibration of a bi-directional functionally graded (BFG) based on a three-layered nonlinear elastic foundation within the framework of the modified couple stress (MCS) theory. The nonlinearity due to the stretching effect of the mid-plane of the BFG microbeam is the source of the nonlinearity of the assumed free vibration issues. The motion governing equations and the corresponding boundary conditions are derived by applying the principle which is associated to Hamilton, under the assumption that the axial inertia is negligible. By applying cubic nonlinearity via Galerkin’s method, the partial nonlinear differential equation can be reduced and turned into an ordinary nonlinear equation of the differential. Then, Galerkin’s variational method is used to gain proximate analytical expressions for the nonlinear frequency of microbeams with boundary conditions of pinned–pinned ends and clamped–clamped ends. The precision of the present solution is evaluated through comparing the nonlinear frequency provided by the proposed approach with the results available from previous studies. The influence of changes in some parameters such as amplitude ratio, the material length scale parameter, material gradient parameters, end supports and stiffness coefficients of the foundation with nonlinearity on the normalized fundamental frequency is studied in detail. As a main result, it is observed that the nonlinear vibration frequencies are higher than their linear counterparts.

In this research paper, the determination of thermal expansivity and thermal conductivity has been accomplished for Al 6061, Silicon Carbide and Graphite hybrid metal matrix composites from room temperature to $300^{\circ }$C. Aluminium-based composites reinforced with Silicon Carbide and Graphite particles have been prepared by stir casting technique. The thermal expansion and thermal conductivity properties of hybrid composites with different percentage compositions of reinforcements have been investigated. The results have indicated that the thermal expansivity and thermal conductivity of the different compositions of hybrid MMCs decrease by the addition of Graphite with Silicon Carbide and Al 6061. Few empirical models have been validated for the evaluation of thermal expansivity and thermal conductivity of hybrid composites. Using the experimental values, namely modulus of elasticity, Poisson ratio and thermal expansivity, computational investigation has been carried out to evaluate the thermal parameters, namely thermal displacement, thermal strain and thermal stress. Similarly, using the experimental values, namely density, thermal conductivity, specific heat capacity and enthalpy at varying temperature ranges, computational investigation has been carried out to evaluate thermal gradient and thermal flux.

A finite element-based numerical method is applied to predict the possibility of propagation of existing delamination/patch in a filament wound composite pressure vessel in this work. Strain energy release rates (SERRs’) in the three principal modes are predicted along the circumference of delamination for two different load cases, i.e., internal pressure load when two diametrically opposite patches are existing in the nozzle end side dome portion, and combined load due to thrust and bending when a patch is located in the nozzle end side skirt region of the composite pressure vessel (CPV). The problem is modeled in ANSYS software and a three-dimensional finite element approach in association with virtual crack closure technique (VCCT) is used to analyze the fracture behavior of the CPV under two load cases as stated. In both the load cases, SERR is found to be maximum at the bottom side of the patch, Mode-I being dominant under pressure load, and Mode-II in axial load. Delamination growth is observed at 26.5% of applied pressure in Case-1 and 57.5% of axial load in Case-2. This fracture analysis approach can be extended to composite structural components in defense and aerospace applications.

In this paper, the structural genome approach is used for multiscale analyses to predict the mechanical and thermal properties of particle reinforced hydrogel composites. First, the structure genome model of particle reinforced hydrogel composites is created by the random sequential adsorption algorithm. Then the mechanical properties and equivalent thermal conductivity of hydrogel composites are numerically studied by the structural genome approach. The effects of particles with different volume fractions and material properties on their mechanical and thermal properties are investigated. From the simulation results, it can be found that within a certain range of volume fraction, the mechanical properties and equivalent thermal conductivity of hydrogel composites are positively correlated with the volume fractions of particles. We also find that with the increase of the mechanical properties and thermal conductivity of particles, the properties of hydrogel can be improved and eventually reach stabilization. The structural genome approach shows excellent efficiency in multiscale structure analysis. It is a convenient method for the simulation of complex soft material composites.

Numerical solutions for a class of unsteady modified Helmholtz problems of anisotropic functionally graded materials are sought. The governing equation which is a variable coefficients equation is transformed to a constant coefficients equation. The time variable is transformed using the Laplace transform. The resulted partial differential equation of constant coefficients and time free variable is then converted to a boundary integral equation, from which boundary element solutions can be obtained. Some examples are considered to verify the accuracy, convergence and consistency of the numerical solutions. The results show that the numerical solutions are accurate, convergent and consistent.

According to the firs-principles theory-based spin-density functional calculations within the framework of Wu–Cohen generalized gradient approximation (WC-GGA), we examine the structural and electronic properties of ternary alloys of zinc-blende boron phosphide doped with chromium. We compare the materials with aluminum phosphide that exhibits half-metallic properties at various concentrations. The curves of total and partial densities of states and the band structures show that ${\text{B}}_{1-x}$${\text{Cr}}_x$P are purely metallic and can be possible candidates for use in light emitting diodes (LEDs). These compounds are not polarized on spins; the main cause is the nature of chemical bond located between the boron cations and the phosphorus anion, whereas the ternary materials of ${\text{Al}}_{1-x}$${\text{Cr}}_x$P all have various uses in spintronic science according to many studies because of their half-metallicity behavior.