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See detailLes matrices métalliques et céramiques : de nouveaux matériaux composites
Montrieux, Henri-Michel ULg; Lecomte-Beckers, Jacqueline ULg; Mertens, Anne ULg

in Plus Composites (2013), article n°3

Le présent article décrit différentes limitations des matériaux composites à matrice polymère. Outre l’amélioration de la formulation des résines, une des alternatives qui se présente est d’employer une ... [more ▼]

Le présent article décrit différentes limitations des matériaux composites à matrice polymère. Outre l’amélioration de la formulation des résines, une des alternatives qui se présente est d’employer une matrice métallique ou céramique. Certains de ces matériaux nouveaux sont toujours au stade du développement. Il s’agit par exemple des composites pour applications structurales avec une matrice légère en aluminium ou en magnésium pour lesquels les rapports rigidité-poids et résistance-poids sont élevés. La résilience est aussi améliorée par rapport aux matrices classiques simplement renforcées. D’autres composites à matrice métallique tels que les cermets sont industrialisés comme outils de coupe. Des composites à matrice céramique comme le carbone-carbone ou le carbone-SiC peuvent être industrialisés et présentent une durabilité et une température d’utilisation maximale exceptionnelle. Pour terminer, l’article fournit quelques informations sur les techniques nouvelles de mise à forme des matériaux composites telles que le friction stir processing et l’additive manufacturing. [less ▲]

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See detailOn the Role of Out-of-Equilibrium Microstructures in Ti-6Al-4V and in Stainless Steel 316L Processed by Selective Laser Melting in Determining their Mechanical Properties
Mertens, Anne ULg; Reginster, Sylvie ULg; Paydas, Hakan ULg et al

Conference (2013, September 12)

Additive manufacturing processes such as Selective Laser Melting (SLM) appear very promising in view of the economic production of near-net-shape, complex and (almost) fully dense parts from metallic ... [more ▼]

Additive manufacturing processes such as Selective Laser Melting (SLM) appear very promising in view of the economic production of near-net-shape, complex and (almost) fully dense parts from metallic materials such as Ti alloys and stainless steels. Practically, in SLM, a metallic powder is deposited layer-by-layer in a powder bed and then molten locally according to the desired shape. An important feature of this process is that the structure undergoes an ultra-fast cooling once the beam leaves the working zone, thus giving rise to strongly out-of-equilibrium microstructures. In the case of Ti alloy Ti-6Al-4V, in particular, the microstructural anisotropy resulting from the epitaxial growth of the newly deposited layer on the material previously solidified has been shown to exert a very strong influence on the mechanical properties [1]. In the present work, the microstructures and mechanical properties of Ti-6Al-4V and of stainless steel 316L processed by SLM have been characterised in details. Since these two materials exhibit quite different physical behaviours, their careful comparison might shed more light into the role of phenomena such as epitaxial growth, out-of-equilibrium phase transformation and/or internal stresses in determining the mechanical properties of metallic parts processed by SLM. [less ▲]

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See detailStudy of phase transformations within bimetallic rolling mills
Neira Torres, Ingrid ULg; Lecomte-Beckers, Jacqueline ULg; Tchuindjang, Jérôme Tchoufack ULg et al

Scientific conference (2013, September 10)

With the aim of simulating the cooling behavior after a re-austenitizing stage of bimetallic rolling mills, both materials corresponding to spheroidal graphite iron (core material) and high chrome steel ... [more ▼]

With the aim of simulating the cooling behavior after a re-austenitizing stage of bimetallic rolling mills, both materials corresponding to spheroidal graphite iron (core material) and high chrome steel (shell material) must be characterized through thermo physical and mechanical tests as well as microscopic observations. Dilatometer tests were carried out for both materials in order to determinate thermo physical properties such as thermal expansion coefficient and density. Compression tests were also performed in order to estimate the effect of mechanical stress on martensite phase transformation, especially the nature and the type of martensite and start of transformation temperature. However there are some parameters that are still unknown and that are highly difficult to determinate. Inverse simulations are performed through Lagamine code with the aim of finding an estimated value for these parameters or improved parameters, more accurate than the ones already estimated. [less ▲]

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See detailMicrostructure and Thermomechanical Behaviour of Magnesium – C nanotubes Composites produced by Friction Stir Processing
Mertens, Anne ULg; Simar, Aude; Garray, Didier et al

Conference (2013, September 09)

Due to their exceptional mechanical and thermal characteristics, C nanotubes (CNTs) are attracting an ever increasing interest in view of tailoring the properties of metal matrix composites (MMCs) e.g ... [more ▼]

Due to their exceptional mechanical and thermal characteristics, C nanotubes (CNTs) are attracting an ever increasing interest in view of tailoring the properties of metal matrix composites (MMCs) e.g. for applications at high service temperature or in thermal management… However, the poor wettability of CNTs by molten metals and their strong tendency to agglomerate are major obstacles to the large-scale production of CNTs-MMCs by classical ‘liquid-state’ processing routes such as squeeze casting. As an innovative ‘solid state’ process, Friction Stir Processing (FSP) hence appears as a very promising alternative for the production of CNTs-MMCs [1], although the method for inserting the reinforcing phase - in grooves or holes machined in the matrix material - remains time-consuming and labour-intensive. More recently, Mertens et al. [2] proposed a new and easier technique for the insertion of C fibres in FSPed Mg-matrix composites i.e. FSP of a C fabric stacked between two metal sheets. In the present work, the feasibility of extending this latter method to the production of CNTs-MMCs has been assessed. “Bucky papers” – made from agglomerated CNTs, thus ensuring for their safe handling – were stacked between two sheets of Mg alloy AZ31B, and the resulting sandwich was FSPed. The effect of FSP experimental parameters such as the rotational and advancing speeds, and the number of FSP passes, on the microstructure of the composites and particularly on the distribution of the CNTs in the Mg matrix has been carefully studied. Moreover, a particular attention has been given to the characterization of the thermomechanical behaviour of the FSPed AZ31B-CNTs composites. [less ▲]

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See detailComparison between optical pulsed thermography and vibrothermography for the assessment of carbon fibers composite materials
Montrieux, Henri-Michel ULg; Demy, Philippe; Ibarra-Castanedo, Clemente et al

(2013, August 02)

Pulsed thermography and vibrothermography are two active thermography techniques characterized by different heating methods of the specimen. In pulsed phase thermography, a sample is heated by two flash ... [more ▼]

Pulsed thermography and vibrothermography are two active thermography techniques characterized by different heating methods of the specimen. In pulsed phase thermography, a sample is heated by two flash lamps for a short period to inject a Dirac impulse heat in the material. The cooling of the part is monitored with an infrared camera to detect thermal contrast in the image, characteristic of the presence of a defect. In vibrothermography, high frequency vibrations are injected into the sample causing an internal heating observed on surface right above the defect due to diverse phenomena as friction or viscoelastic hysteresis. If pulsed thermography is a well-known technique that has been integrated into the arsenal of industrial NDT methods, vibrothermography is a less common experimental method still subject to theoretical and practical investigations. This article aims to compare the effectiveness of the two methods in the case of different types of composites based on carbon fibers: carbon fiber reinforced plastic (CFRP) plates as well as a completely new material: carbon magnesium composite. [less ▲]

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See detailResearch on durable junction of multimaterials
Lecomte-Beckers, Jacqueline ULg; Lecomte, Jacky; Gerlach, Nathalie ULg et al

Poster (2013, April 04)

This collective project aimed to assess the potential of adhesive bonding in various applications in the field of building construction. This evaluation takes into account technical, economical and ... [more ▼]

This collective project aimed to assess the potential of adhesive bonding in various applications in the field of building construction. This evaluation takes into account technical, economical and ecological aspects and provides a methodology that can be easily transferred to other applications. [less ▲]

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See detailRapport Final, Projet Région wallonne R.RWAL.2626-J-F-D, RONDUJUM : Research ON DUrable JUnction of Multimaterials
Lecomte-Beckers, Jacqueline ULg; Gerlach, Nathalie ULg; Lecomte, Jacky

Report (2013)

Le présent projet s’inscrit dans le cadre du développement de matériaux avancés, toujours plus performants, et de leur utilisation dans tous les secteurs industriels, et plus particulièrement dans le ... [more ▼]

Le présent projet s’inscrit dans le cadre du développement de matériaux avancés, toujours plus performants, et de leur utilisation dans tous les secteurs industriels, et plus particulièrement dans le domaine du bâtiment. L’intégration de ces matériaux fait appel à des techniques d’assemblage dont il est essentiel de maîtriser la fiabilité et la durabilité. Le projet vise à fournir aux industriels du secteur des outils pour l’évaluation et la comparaison technique, économique et environnementale de systèmes d’assemblage par collage de matériaux différents dans le domaine du bâtiment. Ce projet est financé par la Région wallonne, soucieuse de soutenir ses industries dans le cadre du redéploiement économique de la Région. L’objectif poursuivi par les centres participants est d’acquérir et de synthétiser des connaissances suffisantes dans le domaine de l’assemblage par collage, de manière à aider les industriels du secteur à effectuer des choix technologiques pertinents et durables, mais aussi à évaluer le coût de mise en oeuvre de ces choix et leur impact économique. Le projet s’appuie sur des exemples d’application pertinents fournis par les industriels du secteur, représentatifs des matériaux et des applications. [less ▲]

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See detailRapport Final, Projet BLISK, Convention RW 6247 : BLaded dISK
Lecomte-Beckers, Jacqueline ULg; Paydas, Hakan ULg

Report (2013)

L’unité MMS de l’ULg s’est concentrée dans le cadre de ce projet sur les aspects métallurgiques des composants produits de manière à garantir dès le départ leur qualité et ainsi adapter les paramètres de ... [more ▼]

L’unité MMS de l’ULg s’est concentrée dans le cadre de ce projet sur les aspects métallurgiques des composants produits de manière à garantir dès le départ leur qualité et ainsi adapter les paramètres de fabrication. D’autre part, elle a également étudié les relations microstructures – propriétés mécaniques et s’est occupée de la caractérisation mécanique et thermophysique des composants soudés par friction et claddés dont la structure a été analysée. [less ▲]

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See detailPrediction of residual stresses by FE simulations on bimetallic work rolls during cooling
Neira Torres, Ingrid ULg; Gilles, Gaëtan ULg; Tchuindjang, Jérôme Tchoufack ULg et al

in Computer Methods in Materials Science (2013), 13(1), 84-91

Bimetallic rolls used in the roughing stands of the Hot Strip Mill require mixed properties as a high wear resistance for the shell material and an enhanced toughness for the core material. The bimetallic ... [more ▼]

Bimetallic rolls used in the roughing stands of the Hot Strip Mill require mixed properties as a high wear resistance for the shell material and an enhanced toughness for the core material. The bimetallic roll studied in this paper is obtained from a vertical spin casting process followed by cooling and subsequent heat treatments. Failure of the compound roll sometimes occurs during the cooling stage of the casting route or later during the thermal treatments. It requires to deeply investigate the thermo mechanical metallurgical interactions generated during cooling and heat treatment in order to find the origin of cracks. For this purpose, a thermo metallurgic mechanical finite element model is used. However these numerical simulations require a high amount of mechanical, thermal and metallurgical parameters. In order to determinate these parameters, a study of available data for estimation of mechanical parameters was performed. Thermo physical parameters were obtained by DTA and DSC methods. Metallurgical characterization by inverse numerical method based on available CCT diagrams was performed to determine the TTT diagrams. First cooling numerical simulations are presented, allowing a rough estimate of residual stresses values and the identification of key parameters for predicting accurate residual stresses by sensitivity analysis. [less ▲]

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See detailTooling Materials and Solutions for Thixoforming of Steel
Rassili, Ahmed ULg; Falzone, Salvatore ULg; Lecomte-Beckers, Jacqueline ULg

in Solid State Phenomena (2013), 192-193

The aim of this work is to evaluate the thermal and mechanical loadings applied to the tools during steel thixoforming process in order to determine appropriate tool materials and solutions. This ... [more ▼]

The aim of this work is to evaluate the thermal and mechanical loadings applied to the tools during steel thixoforming process in order to determine appropriate tool materials and solutions. This evaluation was realized thanks to experimental trials and to the finite elements simulations. The effect of these loadings on the tool’s failure modes are highlighted and compared to the ones observed in classical forming processes. Beyond this, the failure modes of different tool materials and solutions are presented. The tested materials are hot-working tool steels. Other possibilities and tool coating or surface treatments are discussed as well. [less ▲]

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See detailProcessing of Ti alloys by additive manufacturing: a comparison of the microstructures obtained by laser cladding, selective laser melting and electron beam melting
Reginster, Sylvie ULg; Mertens, Anne ULg; Paydas, Hakan ULg et al

in Materials Science Forum (2013), 765

Additive manufacturing processes such as laser cladding (LC) or selective laser melting (SLM) appear very promising in view of an economic near-net-shape production – and also, in the case of LC, the ... [more ▼]

Additive manufacturing processes such as laser cladding (LC) or selective laser melting (SLM) appear very promising in view of an economic near-net-shape production – and also, in the case of LC, the restoration - of complex and (almost) fully dense parts from Ti alloys. Both techniques involve the melting of a metallic powder with a laser. In the SLM process, the metallic powder is deposited layer by layer in a powder bed and then molten locally according to the desired shape, whereas in LC, the metallic powder is directly projected onto a substrate through a nozzle coaxial with the laser beam. The present research aims at comparing Ti-6Al-4V samples processed by these two techniques with reference samples produced by electron beam melting (EBM), another well established additive manufacturing process (patented by Arcam AB Company) in which a powder bed is molten locally by means of an electron beam. In all three processes, the melt pool undergoes an ultrafast cooling and solidifies very rapidly once the beam has left the area, thus giving rise to strongly out-of-equilibrium microstructures. Yet, each one of these processes also has its own specificities e.g. in terms of scanning strategy and of working atmosphere (low vacuum vs. protective Ar flow). In the present work, the microstructures obtained by these three processes have been compared in details, with a particular attention for characteristics such as porosity, grain size, and the various phases present. Since epitaxial growth of the newly deposited layer on the material previously solidified has been shown [1, 2] to exert a strong influence on the microstructure and on the resulting mechanical properties, great care has been taken to study the microstructural anisotropy associated with each one of the three processes. [less ▲]

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See detailDéveloppement d’une ailette d’obus en composite magnésium renforcé de fibres de carbone
Montrieux, Henri-Michel ULg; Mertens, Anne ULg; Lecomte-Beckers, Jacqueline ULg

Report (2012)

This report describes the accomplished breakthrough for the manufacturing of long carbon fibres reinforced magnesium alloy (AZ91). Infiltration can be performed with non-equilibrium conditions such as ... [more ▼]

This report describes the accomplished breakthrough for the manufacturing of long carbon fibres reinforced magnesium alloy (AZ91). Infiltration can be performed with non-equilibrium conditions such as fibres preheating, high liquid compacting pressure and low contact times. Thanks to specific TEOS sol/gel treatment, the reached fibre rate is 60 vol.% and the measured Young's modulus of the composite is ca. 110 GPa. The presence of defects including fibre yarns misorientation, unreinforced areas seems very detrimental to the bending properties. Other advanced infiltration techniques with Al pretreatment (K2ZrF6) of fibres is also considered. [less ▲]

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See detailInfluence of Fiber Distribution and Grain Size on the Mechanical Behavior of Friction Stir Processed Mg-C Composites
Mertens, Anne ULg; Montrieux, Henri-Michel ULg; Lecomte-Beckers, Jacqueline ULg et al

Conference (2012, November 12)

Short C fibers-Mg matrix composites have been produced by friction stir processing sandwiches made of a layer of C fabric stacked between two sheets of either the ductile Mg alloy AZ31B, or of the less ... [more ▼]

Short C fibers-Mg matrix composites have been produced by friction stir processing sandwiches made of a layer of C fabric stacked between two sheets of either the ductile Mg alloy AZ31B, or of the less ductile alloy AZ91D, that is capable of age hardening. It has been shown that the choice of the optimal experimental parameters for the production of sound composites was strongly dependent on the nature of the matrix. 3D X-ray tomography reveals that the fibers orient along the onion rings and that they are more or less fragmented depending on the local shear stress during the process. The fiber volume fraction is increased when the nugget volume decreases in particular for the AZ91D base material and for a high advancing speed for the AZ31B base material. The fiber volume fraction influences directly the grain size, the hardness and the tensile properties of the composites. [less ▲]

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See detailComposite Manufacturing by Friction Stir Processing
Simar, Aude; de Meester, Bruno; Delannay, Francis et al

Conference (2012, October 29)

A new solid-state process developed recently on the same principles as Friction Stir Welding (FSW), Friction Stir Processing appear as a very promising technique for the production of metal matrix ... [more ▼]

A new solid-state process developed recently on the same principles as Friction Stir Welding (FSW), Friction Stir Processing appear as a very promising technique for the production of metal matrix composites and for tailoring materials properties. In the present work, this process has been applied to two different composite systems: (i) magnesium-matrix composites reinforced with carbon fibers, and (ii) copper-matrix composites reinforced with Y2O3 powder. Process optimization and mechanical properties of the composites are discussed in both systems. [less ▲]

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See detailExperimental Characterisation of Damage Occuring during Single Point Incremental Forming of a Ferritic Steel
Mertens, Anne ULg; Guzmán Inostroza, Carlos Felipe ULg; Habraken, Anne ULg et al

Poster (2012, September)

Single Point Incremental Forming (SPIF) has been developed as a new dieless process for forming metal sheets. This technique appears very promising in view of the current requirements for rapid ... [more ▼]

Single Point Incremental Forming (SPIF) has been developed as a new dieless process for forming metal sheets. This technique appears very promising in view of the current requirements for rapid prototyping and/or small series production [1]. However, inaccuracies in the shape of the processed part and material failure constitute important limiting factors for applications. In the present research, a numerical approach, based on the damage model proposed by Gurson [2], has been chosen to analyse and optimise the process, predict the material rupture and the process limit. From experimental observations of plastic deformation and ductile fracture, damage is related to the nucleation, growth and coalescence of microvoids [3]. Gurson’s model uses the volume fraction of these voids as a main variable. Hence the determination of this value is a key factor for a correct identification and validation of the model. More particularly, the present work focuses on two different methods used to experimentally characterise damage occurring during single point incremental forming of a ferritic steel. Void measurements carried out by optical microscopy combined with image analysis have been compared with porosity values obtained from density measurements based on the Archimedes’ principle [4], so as to assess the feasibility of using this method for a quick characterisation of the damage. [less ▲]

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See detailFriction Stir Processing of Magnesium Matrix Composites reinforced with Carbon Fibres: Influence of the Matrix Characteristics and of the Processing Parameters on Microstructural Developments
Mertens, Anne ULg; Simar, Aude; Montrieux, Henri-Michel ULg et al

in W.J.Poole, K.U.Kainer (Ed.) Proceedings of the 9th International Conference On Magnesium Alloys and their Apllications (2012, July 12)

Processing of magnesium matrix composites reinforced with C fibres by ‘liquid state’ methods such as squeeze casting are usually impaired by the poor wettability of C substrates by liquid Mg. As a ... [more ▼]

Processing of magnesium matrix composites reinforced with C fibres by ‘liquid state’ methods such as squeeze casting are usually impaired by the poor wettability of C substrates by liquid Mg. As a consequence, ‘solid state’ processes such as Friction Stir Processing (FSP) appear as very promising alternative processing routes for the production of C-Mg composites. And, more particularly, FSP of a C fabric between two sheets of the fairly ductile Mg alloy AZ31B was shown to be a simple and innovative process for a large-scale production of magnesium matrix composites reinforced with short C fibres. In the present work, FSP of a C fabric between two metal sheets or thin plates has been performed using two different Mg alloys exhibiting quite different mechanical behaviours, i.e. alloy AZ31B and the more brittle alloy AZ91D. And the effect of the matrix characteristics, along with the influence of the FSP experimental parameters such as the rotational and advancing speeds, on the microstructural changes occuring upon processing have been carefully studied. A particular attention has been given to the fragmentation and distribution of the C fibres, as well as to the recrystallisation, solutionising and precipitation processes taking place in the Mg matrix. [less ▲]

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See detailInfluence of the addition of functionalized MWCNT on mechanical properties on epoxy/carbon fiber and epoxy/carbon-aramid fiber composites
Fernandez, Carolina; Flores, Paulo; Montrieux, Henri-Michel ULg et al

in Proceedings of the 1st Brazilian Conference on Composite Materials (2012, July)

We investigated the effect of the inclusion of carbon nanotubes (CNT) on the mechanical properties and wear behavior of epoxy/carbon and epoxy/carbon-aramid composites in this study. Epoxy/carbon and ... [more ▼]

We investigated the effect of the inclusion of carbon nanotubes (CNT) on the mechanical properties and wear behavior of epoxy/carbon and epoxy/carbon-aramid composites in this study. Epoxy/carbon and epoxy/carbon-aramid composites with 0 wt.% CNT and 0.3 wt.% CNT were manufactured by RTM, amino functionalized multi-walled CNT (MWCNT) were used to modify the matrix. Tensile, compression, two rail shear, Charpy impact tests and Pin On Disc (POD) were performed on the four composites. The EP/CAF composites showed better impact resistance than the ones containing carbon woven. The addition of CNTs improves the shear modulus in 5% for EP/CF composites and 6% for EP/CAF. The results also show that the dynamic friction coefficient is independent of the CNT content, and the specific wear rate shows no improvement with the selected test parameters. [less ▲]

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