Hypothesis: In elastomeric composites, interfacial phenomena such as the effect of reinforcing filler on molecular dynamics of the rubber chain in the interphase and the way of rubber-filler interaction are the source of strain energy change or viscoelastic loss of the composite in highly filled rubber compound. To obtain a preliminary approximation of how the strain energy is influenced by interfacial phenomena, including stiffness, loss and the quality of this region, in this research, the finite element microstructural model was created in two-dimensional and three-dimensional mode and the effective characteristic changes in mechanical properties were studied. The effect of the change in stiffness of the interphase and the change in viscoelastic nature, the amount of contact between the rubber-filler in completely bonded and frictional sliding states were modeled.Methods: The solution styrene butadiene rubber composites reinforced with silica were prepared by melt mixing. For this purpose, rubber was mixed with silica and silane coupling agent in an internal mixer. Then the masterbatch was mixed with the curing system on a two-roll mill and finally the sample was cured under pressure at 160°C.Findings: In agreement with the modeling results, the composite tensile test showed that the most important controlling parameter is the type of rubber-filler connection in the interphase. The simulation results showed that considering the interphase region with frictional sliding greatly reduces the stress transfer from the matrix to the particle. But in the case of the completely bonded interphase region, due to the complete transfer of stress from the particle to the matrix, the mechanical properties showed a significant deviation compared to the experimental results. Also, the 3D models provided better predictions than the 2D ones.

Carbon nanotube, a product of chemical exfoliation of graphite, is a suitable additive for use as nanoreinforcement in cement-based materials due to its high aspect ratio, good water dispersibility and excellent mechanical properties. In the present study, the effect of volume fraction, aspect ratio, distribution orientation and interaction between surfaces on the mechanical properties of cement matrix reinforced with carbon nanotubes using Multi-scale modeling was investigated. To Model in the Abaqus software, with the conceptual understanding of the volume representative element, a developed MATLAB and Python scripts were applied. To observe the interphase behavior between the matrix and fillers, the cohesive surface theory was used. Also, the output results of molecular dynamics modeling was used to determine the cohesive surface parameters. modeling was done in the states of full and limited bonding between two phases in nano-compsite with compressive axial loading. The cement models with 0, 0.5, 1, and 1.5 vol% with aspect ratios of 10 and 20 were evaluated and discussed. Furthermore, the distribution effect was studied by defining the nanotubes to be parallel, perpendicular and random regarding the force direction. The results showed that increasing the volume fraction of CNTs improves the yield strength and toughness of the samples. Increasing the CNT aspect ratio from 10 to 20 leads to an increase of elastic limit and an improvement of plastic behavior of the next matrix. Finally, the cohesive modeling of the interactions of matrix and CNT eventuated in 3 to 6% reductions per 0.5 and 1% CNT/cement composites.

In this paper, multiscale modeling of Epoxy-based hybrid nanocomposites was performed. Single-walled carbon nanotube and carbon nanoparticle (diamond) were used as reinforcements and the elastic behavior of hybrid nanocomposite was investigated. In the multiscale modeling, at the nanoscale and pico-second time range, molecular dynamics method was used to make an accurate model of the interaction between the nano-scale reinforcements and the polymer matrix to predict the interface behavior more realistically. At the micro and macro scales, micromechanical models were used to predict the elastic properties of the nanocomposites, incorporating the effects of interface behavior. Finite element method was also used to check the accuracy of the results obtained at the macro scale. First, pure thermoset polymer with 75% crosslinking ratio was simulated using molecular dynamics method. Then two nanocomposites, one consisting of a single-walled carbon nanotube and another one containing a carbon nanoparticle (diamond) were simulated to obtain equivalent fiber mechanical properties. Next, a micromechanical model was developed for hybrid nanocomposite using the equivalent fiber and pure thermoset polymer mechanical properties. In addition, the results obtained from the molecular dynamics simulations, along with a correction coefficient were employed in the micromechanical models and finite element simulations. Finally, micromechanical multiscale modeling results were compared with finite element multiscale modeling results and a good agreement was observed. Results suggest that the use of two types of nano-reinforcement together, hybrid nanocomposite, improves nanocomposite mechanical properties.

In this research, mechanical properties and fracture mechanism of polymer Nano composite reinforced by carbon nanotubes (CNTs) has been evaluated employing multiscale modeling method. Effect of CNTs’ structural defects and covalent bonds created during functionalization process are investigated in nanoscale analysis and the effect of CNTs’ dispersion, curvature and volume fraction are studied in microscale analysis. In microscale modeling both analytical and finite element methods are employed to investigate mechanical properties and their results are compared. It has been investigated that, according to mentioned parameters such as CNTs’ dispersion, volume fraction, functionalization and curvature in polymer matrix, both increase and decrease in ultimate strength of polymer nanocomposite are possible with respect to pure polymer. Moreover, polymer nanocomposite’s ultimate strength is increased and fracture brittleness is decreased significantly using functionalized CNTs. On the other hand, the CNT’s structural defects caused during functionalization process decrease polymer nanocomposite Young’s modulus. It also has been demonstrated that by increasing curvature, the improving effects of functionalized CNTs on mechanical properties of polymer nanocomposite, decrease obviously.

This paper introduces dimensional and numerical investigation of the problem of solute transport within the two-phase flow in a porous cavity. The model consists of momentum equations (Darcy’ s law), mass (saturation) equation, and solute transport equation. The cavity boundaries are constituted by mixed Dirichlet-Neumann boundary conditions. The governing equations have been converted into a dimensionless form such that a group of dimensionless physical numbers appear including Lewis, Reynolds, Bond, capillary, and Darcy numbers. A time-splitting multiscale scheme has been developed to treat the time derivative discretization. Also, we use the Courant-Friedrichs-Lewy (CFL) stability condition to adapt the time step size. The pressure is calculated implicitly by coupling Darcy’ s law and the continuity equation, then, the concentration equation is solved implicitly. Numerical experiments have been conducted and the effects of the dimensionless numbers have been on the saturation, concentration, pressure, velocity, and Sherwood number have been investigated.

In the present research, a multiscale method based on crystal plasticity finite element method and computational homogenization is proposed to simulate monotonic and cyclic plastic deformation of a highly textured rolled magnesium alloy AZ31. All active deformation mechanisms including slip, twinning as well as detwinning have been simulated in the model through user material subroutine in ABAQUS (UMAT). All representative volume elements have been constructed, synthetically. Polycrystal laminate has been reproductive by representative volume element (RVE) and periodic boundary conditions have been applied on the RVE faces. For cyclic validations, uniaxial compression-tension along extrusion direction has been applied for 2 loading cycles and the problem at the macroscopic scale has been solved by the ABAQUS finite element solver. The results are in good accordance with the experimental curves and the proposed model can accurately predict all cyclic behavior characteristics like asymmetry in a stress-strain curve due to alternating twinning-detwinning, tensile and compressive peak stresses, twinning and detwinning.