Three-Dimentional Textile Preform Using Advanced Textile Technologies for Composite Manufacturing

Textile reinforcement structure plays an important role in the reinforcement/composite performances during the composite manufacturing and in-service life of the composite material. Structures with a three-dimensional (3D) fiber topology are desired due to their superior multiaxial performance and efforts have been made to modify 2D textile technologies to produce complex 3D shapes. Most of these 3D solutions are based on the principle of adding out-of-plane reinforcements to a planar 2D fabric. Well-established 3D textile methods such as braiding and knitting have also been demonstrated to directly produce near net-shape structures. To understand these potentialities, the first section of this chapter will present the several textile technologies with strengths and weaknesses of these processes to manufacture technical reinforcements for composite applications. In the following sections, several applications with specific textile architectures will be given, in particular, the applications of the through-the-thickness reinforcement and 3D textile ply during the composite manufacturing

A quasi-Monte Carlo integration method applied to the computation of the Pollaczek integral

Nos remerciements à IEEE pour l'autorisation de mise à disposition du papier complet. © IEEE Copyright Notice : Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.International audienceThis paper presents an effective numeric method to compute Pollaczek integral. This integral is widely used in transmission-line theory when computing the mutual impedance between an overhead conductor and another overhead or underground conductor and the earth-return impedance of an underground cable. At first, we present mutual expressions proposed by Pollaczek and underline the numerical complexities that often lead to the adoption of alternative simplified methods. Then a brief review of the so called "quasi-Monte Carlo" integration method along with its advantages is given. Such an approach is then applied to compute numerically Pollaczek expressions. Comparison between our numerical procedure and an algorithm that has already been published proves both the procedure accuracy, one of its main advantages along with its ease of implementation, and its relatively low time consumption, independent of the input parameters. Finally, as an application example, quasi-Monte Carlo method is used to assess the adequacy, for several study cases, of the simplified formula by Lucca, which is a widely used approximate expression of interest

Hybrid control with on/off electropneumatic standard valve for tracking positioning

International audienceThis paper presents a new method of control applied in electropneumatic field. This strategy is issued from hybrid control theory recently applied in control of asynchronous or synchronous electrical motor (1, 2). The interest of these procedure concerns the possibility of controls the position of an electropneumatic piston all along the cylinder stroke with standard on/off valve. Nowadays the industrial electropneumatic process used on/off valve for point to point aim with displacement from one extremity of cylinder to the other one. When different desired positions are required the constructors used specific components issued from proportional technology: servovalve or servodistributor for example. The evolution in the automation process is moving towards a need of obtaining greater versatility and increased precision in compressed air driven equipment. This means obtaining proportional operation of the power element as a function of an electric control signal. Nevertheless, when the desired precision is near the millimetre and not very good performances are need during dynamic stage, the useful of proportional technology can be debatable. Indeed the system cost and its complexity to tune can be two drawbacks that on/off technology with the proposed algorithm, can be concurrence. Based on both the models of cylinder and valves, the hybrid control presented here determines the best state of valves by tracking reference values of the cylinder states in the state space. Then a simplified model of electropneumatic system is presented and used to synthesised hybrid control algorithm. Experimental results are presented and discussed

Analysis of the blank holder force effect on the preforming process using a simple discrete approach

Simulation of the dry reinforcement preforming, first step of the Resin Transfer Moulding process, become necessary to determine the feasibility of the forming process, compute the fiber directions in the final composite component, and optimize process parameters during this step. Contrary to geometrical approaches, based on fishnet algorithms [1, 2], finite element methods can take into account the actual physical parameters, the real boundary conditions and the mechanical behaviour of the textile reinforcement [3, 4]. The fabric can be modelled either as continuum media with specific material behaviour [5, 6], or using discrete structural elements to describe the textile structure at the mesoscopic scale [7, 8]. A semi-discrete approach, which is a compromise between the above continuous and discrete approaches [9, 10], is also used for simulation. A discrete approach for the simulation of the preforming of dry woven reinforcement has been proposed and presented in a previous paper [11]. This model is based on a “unit cell” formulated with elastic isotropic shells coupled to axial connectors. The connectors, which replace bars or beams largely studied in other discrete approaches [12], reinforce the structure in the yarn directions and naturally capture the specific anisotropic behaviour of fabric. Shell elements are used to take into account the in-plane shear stiffness and to manage contact phenomena with the punch and die. The linear characteristic of the connectors [11], has been extended to a non linear behaviour in the present paper to better account for fabric undulation. Using this numerical model, we propose, in this work to study the effect of process parameters on the woven fabric deformation during the performing step. The emphasis will be placed on the analysis of the influence of the blank holder pressure on the shear angle distribution.This work has been undertaken within the framework of the Défi composite project. The authors would like to thank Oséo for its financial support, the project leader Airbus-France and other partners (EADS IW and LoireTech) for provided facilities

Building an Observatory of Course-of-Action in Software Engineering: towards a Link between ISO/IEC Software Engineering standards and a Reflective Practice

International audienceAs a help to compete in an evolving market, small software companies may use an observatory of their course-of-action. The course of action considers the observable aspect of the actor's activity. Its analysis provides a description of actors' activity and it can express recommendations concerning both the individual situations and the collective situation. The observatory is an articulated set of data collecting methods supported with semantic wikis and a dedicated application. A case study, based on the activity of a team of 6 young software engineers, depicts some aspects of the building and the filling of the course-of-action observatory. As primary results of this work, we may think that observing and analyzing software engineer's activity help to reveal his/her theory-in-use - what governs engineers' behavior and tends to be tacit structures - That may help engineers to establish links between "Project Processes-in-use" and a simplified Process Reference Model and contribute to reduce the fit between a project-in-action and espoused SE standards

Analyse du comportement en traction de renforts tressés pour application composite

De nombreuses études existent dans la littérature sur les potentialités des tresses utilisées comme renforts dans les composites [1, 2]. Si le comportement mécanique est bien décrit à l'état des composites, peu d'études concernent le comportement mécanique des tresses sèches [3, 4]. Dans le cadre de cette publication, des tresses sont produites avec un multifilament retordu de PEHD (Polyéthylène à haute densité) sur un métier à tresser disponible au laboratoire GEMTEX [5]. Le plan d'expérience consiste à faire varier le nombre de fils et l'angle de tressage. Ce dernier paramètre a un impact déterminant sur les caractéristiques finales de la tresse [6]. Il est contrôlé en faisant varier les paramètres de vitesse de la tresseuse. Deux types de tresses ont été élaborées dans cette étude : biaxiales et triaxiales. Des essais de traction uniaxiale sont effectués, et l'évolution de l'angle de tressage est enregistrée en analysant à intervalles réguliers les images extraites du suivi par vidéométrie. Deux comportements mécaniques peuvent être ainsi distingués. Un premier comportement qualifié de simple pic pour les tresses biaxiales et les tresses triaxiales à angle de tressage faible, le pic de charge provenant de la rupture simultanée de tous les fils. Lorsque les tresses triaxiales sont caractérisées par un angle de tressage élevé, on observe un premier pic associé à la rupture des fils axiaux, puis on constate une seconde évolution de charge due à la rupture des fils de biais. Ce deuxième comportement est qualifié de double pic [7]. Le comportement mécanique en traction est analysé en fonction de la variation de l'angle de tressage et du nombre de fils. Avec la matière utilisée (PEHD), au cours des essais de traction, il est observé un échauffement de la tresse. Cet échauffement est dû, à l'échelle mésoscopique, aux frottements entre les fils, induit par l'évolution de leur position à travers l'effort imposé. Par conséquent, dans le protocole expérimental, est ajoutée une caméra thermique afin de suivre cette élévation de température. Elle est synchronisée d'une part avec l'effort imposé mais également avec le suivi de l'angle de tressage. Cet échauffement est analysé en fonction du comportement mécanique, de l'évolution de l'angle de tressage et du nombre de fils. On constate que l'intensité de l'échauffement est lié au nombre de fils, et que sa cinétique d'évolution dépend de l'angle de tressage initial. Références [1] L. Laberge-Lebel and Suong Van Hoa, ?Manufacturing of Braided Thermoplastic Composites with Carbon/Nylon Commingled Fibers,? J. Compos. Mater., vol. 41, no. 9, pp. 1101?1121, 2007. [2] K. Birkefeld, M. Röder, T. von Reden, M. Bulat, and K. Drechsler, ?Characterization of Biaxial and Triaxial Braids: Fiber Architecture and Mechanical Properties,? Appl. Compos. Mater., vol. 19, no. 3?4, pp. 259?273, Feb. 2011. [3] Rawal A, Saraswat H and Sibal A. Tensile response of braided structures: A review. Text Res J 2015; 85: 2083?2096. [4] Rawal A, Sibal A and Saraswat H. Tensile behaviour of regular triaxial braided structures. Mech Mater 2013; 91: 277?289. [5] J.-V. Risicato, F. Kelly, D. Soulat, X. Legrand, W. Trümper, C. Cochrane, and V. Koncar, ?A Complex Shaped Reinforced Thermoplastic Composite Part Made of Commingled Yarns With Integrated Sensor,? Appl. Compos. Mater., May 2014. [6] P. Potluri, A. Rawal, M. Rivaldi, and I. Porat, ?Geometrical modelling and control of a triaxial braiding machine for producing 3D preforms,? Compos. Part A Appl. Sci. Manuf., vol. 34, no. 6, pp. 481?492, Jun. 2003. [7] B. Duchamp, X. Legrand, D. Soulat. The tensile behavior of biaxial and triaxial braided fabrics. Journal of Industrial Textiles, first published on June 16, 2016 as doi: 10.1177/152808371665446

Optimisation des paramètres d'estampage de renforts secs pour applications composites structuraux

Avec des normes européennes de plus en plus restrictives vis-à-vis des émissions de CO2 [1], l'industrie automobile mènent une véritable politique d'allégement de leurs véhicules [2]. Depuis plusieurs décennies, les matériaux composites représentent une réponse aux problématiques d'allègement de structures. La filière automobile française s'intéresse donc à l'industrialisation de leurs procédés de mises en ?uvre, trop souvent peu répétables et limités aux petites et moyennes séries.   Les procédés de type RTM (Resin tranfert Moulding) permettent la production de matériaux composites hautes performances en grande série tout en garantissant une bonne répétabilité. Habituellement, le procédé RTM est décomposé en deux étapes [3]: Mise en forme de renforts fibreux (semi-produits textiles) ou préformage. Injection de la résine (ou imprégnation) dans la préforme.   L'étape de mise en forme de renforts secs selon la géométrie de la pièce joue influe directement sur les paramètres morphologiques de la préforme (orientation, densité et continuité des renforts) qui ont une incidence directe sur la perméabilité de la préforme et sur le comportement mécanique de la pièce composite finale [4]. Dans le cas de l'industrie automobile grand volume, un des procédés de mise en forme privilégiés est l'estampage. Pour respecter du cahier des charges de la préforme et une bonne répétabilité, une montée en maturité de ce procédé est nécessaire.   Dans ce cadre, l'IRT M2P, un centre de recherche, est appuyé par un consortium de 14 industriels (Arkema, Chomarat, Compose, Coriolis, ESI, Faurecia, Hexion, Hutchinson, Institut de Soudure, Owens Corning, PEI, PSA, Renault, SISE) dans le cadre du projet Fast FORM. Ce projet collaboratif ambitionne de développer les méthodes et technologies nécessaires à la réalisation de préformes à destination de l'industrie automobile : Pour pièces structurales de grandes dimensions Optimisation de l'engagement matière Optimum technico-économique Temps de cycle de 2 min  Dans cette communication, les différents maillons de la démarche de montée en maturité du procédé d'estampage seront présentés :   Caractérisation des renforts : permet de fournir une loi matériaux pour la simulation. Un intérêt particulier est porté sur la caractérisation en cisaillement, qui est considéré comme le mode de déformation prépondérant lors du préformage. L'essai de bias test est notamment simulé pour vérifier la bonne corrélation avec l'expérience. Cette communication s'appuiera sur la caractérisation d'un NCF de verre. Réalisation d'estampages de géométries élémentaires (hémisphères, goussets). Ces essais sont simulés sous PAM FORM (ESI Group [5]). La corrélation expériences / simulations permettra d'ajuster les cartes matériaux et d'identifier les leviers d'optimisation. Itération pour définir une configuration d'estampage optimale pour des pièces complexes de grandes dimensions. Cette phase définit la forme des outils et leur cinématique grâce à la simulation sous PAM FORM. Ces définitions permettent de concevoir et d'industrialiser le procédé. Corrélation simulation-expérience d'estampages de grandes dimensions. Cette phase permet de valider les méthodes et la mise en données de l'étude numérique. Références :   [1] European Commission, Press release: Further CO2 emission reductions from cars and vans: a win-win for the climate, consumers, innovation and jobs. 2012. [2] L. David, ?Stratégie Matériaux Automobile pour les années à venir.? PSA / SRA, 12-Jun-2013. [3] P. Boisse, ?Mise en forme des matériaux fibreux - Tech. ing.? 2004. [4] D. Turner and K. Hjelmstad, ?Determining the 3D permeability of fibrous media using the Newton method,? in Compos. Part B Eng., 2007, pp. 44 ? 57. [5] ?https://www.esi-group.com/fr.?

Innate immune recognition of flagellin limits systemic persistence of Brucella

Brucella are facultative intracellular bacteria that cause chronic infections by limiting innate immune recognition. It is currently unknown whether Brucella FliC flagellin, the monomeric subunit of flagellar filament, is sensed by the host during infection. Here, we used two mutants of Brucella melitensis, either lacking or overexpressing flagellin to show that FliC hinders bacterial replication in vivo. The use of cells and mice genetically deficient for different components of inflammasomes suggested that FliC was a target of the cytosolic innate immune receptor NLRC4 in vivo but not in macrophages in vitro where the response to FliC was nevertheless dependent on the cytosolic adaptor ASC, therefore suggesting a new pathway of cytosolic flagellin sensing. However, our work also suggested that the lack of TLR5 activity of Brucella flagellin and the regulation of its synthesis and/or delivery into host cells are both part of the stealthy strategy of Brucella towards the innate immune system. Nevertheless, since a flagellin-deficient mutant of B. melitensis was found to cause histologically demonstrable injuries in the spleen of infected mice, we suggested that recognition of FliC plays a role in the immunologic standoff between Brucella and its host, which is characterized by a persistent infection with limited inflammatory pathology

Molecular Level Characterization of the Structure and Interactions in Peptide-Functionalized Metal-Organic Frameworks

We use density functional theory, newly parameterized molecular dynamics simulations, and last generation N-15 dynamic nuclear polarization surface enhanced solid-state NMR spectroscopy (DNP SENS) to understand graft-host interactions and effects imposed by the metal-organic framework (MOF) host on peptide conformations in a peptide-functionalized MOF. Focusing on two grafts typified by MIL-68-proline (-Pro) and MIL-68-glycine-proline (-Gly-Pro), we identified the most likely peptide conformations adopted in the functionalized hybrid frameworks. We found that hydrogen bond interactions between the graft and the surface hydroxyl groups of the MOF are essential in determining the peptides conformation(s). DNP SENS methodology shows unprecedented signal enhancements when applied to these peptide-functionalized MOFs. The calculated chemical shifts of selected MIL-68-NH-Pro and MIL-68-NH-Gly-Pro conformations are in a good agreement with the experimentally obtained (NNMR)-N-15 signals. The study shows that the conformations of peptides when grafted in a MOF host are unlikely to be freely distributed, and conformational selection is directed by strong host-guest interactions