Olivier Mantaux

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.

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.

Influence of impurities on the performances of HIPS recycled from Waste Electric and Electronic Equipment (WEEE).

In order to produce a high quality recycled material from real deposits of electric and electronic equipment, the rate of impurities in different blended grades of reclaimed materials has to be reduced. Setting up industrial recycling procedures requires to deal with the main types of polymers presents in WEEE (Waste Electric and Electronic Equipment), particularly High Impact Polystyrene (HIPS) as well as other styrenic polymers such as Acrylonitrile-Butadiene-Styrene (ABS), Polystyrene (PS) but also polyolefin which are present into WEEE deposit as Polypropylene (PP). The production of a substantial quantity of recycled materials implies to improve and master the compatibility of different HIPS grades. The influence of polymeric impurities has to be studied since automatic sorting techniques are not able to remove completely these fractions. Investigation of the influence of minor ABS, PS and PP polymer fractions as impurities has been done on microstructure and mechanical properties of HIPS using environmental scanning electron microscopy (ESEM) in order to determine the maximum tolerated rate for each of them into HIPS after sorting and recycling operations.

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.

Information exchanges between experts for thermoset composites design for recycling

The use of composites in industry is ever increasing. However, end-of-life solutions for composites are still under development. In this paper, a solution linking design strategies with a recycling process for thermoset composite materials is proposed. The recovery solution for these materials is a supercritical water solvolysis process. The needs and multi-disciplinary skills required for taking recycling possibilities into account in the early stages of product design and the necessity to standardise product-recycling capabilities based on design requirements will be discussed. The paper highlights the need for designers to take a functional approach into consideration, including characterisation of materials behaviour, recycling process limits, constraints and opportunities. This paper will show the first lessons learned from experiments, using this technique.

Composite Fiber Recovery: Integration into a Design for Recycling Approach

In industry, the use of composites, and more specially carbon fiber/thermoset matrix ones, is ever increasing. However, end-of-life solutions for these materials are still under development. In this chapter, a solution linking design strategies with a recycling process based on the solvolysis of the matrix by water under supercritical conditions is proposed. The needs and multi-disciplinary skills required for (i) taking recycling possibilities into account from the early stages of the product design, and (ii) the necessity to standardize its recycling capabilities with design requirements, will both be discussed. The present chapter highlights the need for designers to take a functional approach into consideration, including material characterization, limits of the recycling process, constraints and opportunities. The first lessons learned from experiments using this technique will be shown.