Transition metal dichalcogenides (TMDs) represent a large family of high-quality 2D materials with attractive electronic, thermal, chemical, and mechanical properties.Chemical vapour deposition (CVD) technique is currently the most reliable route to synthesis few-atomic layer thick and large-scale TMDs films. However, the effects of grain boundaries formed during the CVD method on the properties of TMDs nanomembranes have remained less explored. In this study, we therefore aim to investigate the thermal conduction along polycrystalline molybdenum disulfide (MoS 2 ) as the representative member of TMDs nanomembranes family. This goal was achieved by developing a combined atomistic-continuum multiscale method. In the proposed approach, reactive molecular dynamics simulations were carried out to assess thermal contact conductance of diverse grain boundaries with various defects configurations. The effective thermal conductivity along the CVD grown polycrystalline and single-layer MoS 2 was finally acquired by conducting finite element modelling. Insight provided by this investigation can be useful to evaluate the effective thermal transport along a wide variety of 2D materials and structures.
International audienceThe aim of this work is to focus on the StokesDarcy coupled problem in order to simulate numerically, with the finite element method, composite manufacturing processes based on liquid resin infusion. In this study, a macroscopic description is used. The computational domain can be divided into two non-miscible sub-domains: a purely fluid domain and a porous medium. In the purely fluid domain, the fluid flows according to the Stokes equations, while in the porous medium, the fluid flows into the preforms according to the Darcy equations. Specific conditions have to be considered on the fluid/porous medium interface. The corresponding weak formulation is obtained by summing up the variational forms of the Stokes and Darcy equations over the whole domain. It is solved by a mixed velocity/pressure finite element method. In the purely fluid domain, a first-order mixed P1+/ P1 finite element is used. However, in the porous medium, the LadysenskayaBrezziBabuska stability condition is not satisfied, and a P1/P1 finite element is preferred. It is stabilized with the Hughes Variational Multiscale formulation. The originality of our approach is two fold. First, one single unstructured mesh is considered for the whole domain. Second, the interface between the purely fluid domain and the porous medium is represented by a level-set function. The level-set framework is also used to capture the resin flow front. At the end of this paper, numerical simulations of such manufacturing processes by resin infusion/injection are presented
International audienceThe aim of this paper is to present an overall model for the study of resin infusion based processes, in particular, the impregnation of a liquid resin through dry deformable fibrous reinforcements. This model can be appliedto a wide range of activities in many fields of engineering. Here, our approach based on a monolithic formulation in a level-set framework allows to strongly couple a Stokes-Darcy flow in low permeability media undergoing finite strains. The Stokes-Darcy coupled problem is solved using a mixed velocity-pressure formulation stabilized by a multi-scale method. A key feature of our approach is the fluid-solid interaction leading to couple a fluid/porous flow to a non-linear solid mechanics formulation. The interaction phenomenon due to the resin flow in the orthotropic highly compressible preform is based on both Terzaghi's law and on explicit relation expressing permeability as function of porosity in finite strains mechanical framework. Finally, simulations of industrial design parts are performed to illustrate the abilities of our approach and the relevance of this fluid/porous-solid mechanics coupled problem for composite material process simulations
A comparison between experiment and numerical simulation of microwave heating of a parallelepipedic silicon carbide (SiC) sample is presented. Using a-2.45 GHz single-mode cavity, the evolution of the surface temperature is first experimentally studied for different orientations of the sample. A finite element analysis of this electromagnetic-thermal coupled problem is then conducted with the COMSOL Multiphysics ® software. Despite the different approximations of our model, a good agreement between experimental and numerical results is found, confirming that the heating of SiC depends only on the electric field. The effect of sample orientations and the cavity length on heating is also highlighted and analyzed.
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