Michel Danis

Numerical simulation of metal matrix composites and polymer matrix composites processing by infiltration: a review

The injection of a liquid metal through a fibrous preform is one of the techniques used to manufacture metal matrix composites (MMCs). The flow of metal through fibrous preform is a problem of fluid mechanics in porous medium. Numerical simulations of this process were developed in particular for non-isothermal infiltrations which take into account the phenomena of phase change. In addition, numerical models were developed to predict the appearance of defects in the end product and to study the evolution of the deformation of the fibrous preform during metal infiltration. After pointing out the analogous numerical studies devoted to the Resin Transfer Moulding (RTM) process, we give a progress report on the models developed to date for MMCs.

Metal matrix composite processing: numerical study of heat transfer between fibers and metal

Purpose – To study heat transfer kinetics at the fiber scale in order to describe injection of liquid metal through a fibrous perform initially situated in a preheated mould, which is one of the various methods used in order to produce metal matrix composite materials (MMCs).Design/methodology/approach – The first part presents a preliminary study in a static case to describe heat transfer kinetics between a fiber and the matrix in the case of a sudden contact of both components initially set up at different temperatures. This model enables to study the influence of the various parameters of the problem on heat transfer kinetics with phase change. In the second part, we present a modeling which takes into account the metal convection within the pores of the preform.Findings – The numerical results of these two models justify the instantaneous thermal equilibrium assumption classically admitted to describe MMCs manufacturing methods. The results of this dynamic microscopic model are compared with the resul...

Numerical prediction of microporosity formation during the solidification of a pure metal within a porous preform

During the elaboration of metal-matrix composites (MMCs) by infiltration, the appearance of microporosities is more frequent and more difficult to control than in traditional foundry because the fibrous preform slows down the circulation of the liquid metal. With the aim of modelling solidification shrinkage and its prediction, we will present in this paper an algorithm which takes into account : (i) the volume drop due to the solidification shrinkage, (ii) the nucleation of microporosities and (iii) the apparent compressibility of the liquid. It is demonstrated that the apparent compressibility is due to the presence of gas trapped in the liquid during the impregnation of the preform. Secondly, we will present an experimentation with solidification of molten metal infiltrated into a preform. The solidification of the metal in the preform is presented according to various experimental configurations in order to show the influence of the solidification parameters. Lastly, numerical and experimental results will be compared for conditions with and without riser which validates the numerical model.

Numerical Simulation of Segregation Phenomena Coupled with Phase Change and Fluid Flow: Application to Metal Matrix Composites Processing

The injection of a liquid metal through a fibrous preform, located in an initially preheated mold, is one of the techniques used to manufacture metal matrix composites (MMCs). In order to reduce the chemical reactions between the fibers and the metal matrix, the fibrous reinforcement and the mold are commonly preheated up to initial temperatures much lower than the metal solidification temperature. Therefore, local metal solidification instantaneously occurs on fiber during liquid metal infiltration. When infiltrating metal alloy, unlike what happens when infiltrating a pure metal, both temperature and composition may vary within the matrix; this heterogeneity induces segregation within composites. A fiber scale numerical simulation was developed taking into account coupled physical phenomena which occur during the processing: flow of the liquid metal around the fibers, phase change phenomena, solute redistribution at the liquid/solid interface during alloy solidification, and species diffusion. This model predicts the segregation phenomena associated with fibrous preform infiltration by a binary alloy.

Processing of Metal Matrix Composites: Bidimensional Numerical Model of the Infiltration of Fibrous Preform by a Pure Metal

The infiltration process is one of the techniques employed to work out polymer matrix composites (PMC) or metal matrix composites (MMC) and with continuous reinforcement. It consists in injecting the liquid (resin or metal) through a fibrous reinforcement placed in a mould. In the case of the MMC, the fibres and the mould are initially preheated at temperatures lower than the temperature of metal solidification. These thermal conditions induce phenomena of phase change of metal when the metal is in contact with the fibres. These phenomena disturb the flow of metal through the fibrous network. In order to follow the displacement of metal in the preform and take into account of the phase change, a two-dimensional numerical model based on a finite volume formulation was developed, on a very simple geometry.© 2002 ASME

Influence de la longueur de l'echantillon sur la mesure simulee de conductivite thermique d'un materiau heterogene

Abstract The effects of the heterogeneities of the sample upon the measurement of the apparent thermal conductivity by a non transient method is studied by numerical simulation. The conductivimeter is of the cylindrical type, the sample being maintained by two pieces of high conductivity material. Two types of heterogeneous medium are studied: (i) a stratified medium with the strata parallel to the average flux, (ii) a two-phase granular medium corresponding to the model of a rock sample. The influence of the sample size upon the measured conductivity and the effect of the thermal conductivity of the two conducting blocks are emphasized.

Ecoulement diphasique permanent a bas nombre de Reynolds et bas nombre capillaire dans une succession de divergents-convergents methode de resolution aux differences finies

Abstract Solution for two-phase flow with low Reynolds number and low Capillary number in two-dimensional divergent-convergent channel is presented. The method consists in (1) solving separately in each fluid domain the Navier-Stokes and continuity equations for some velocity conditions on the interface and (2) choosing the solution which appears physically as the most satisfactory relatively to the equality of tangential stresses on both sides of the interface. So, for a given interface, it is possible to determine the pressure drop in such a channel for various viscosity ratios.