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We present in this paper a numerical simulation of the filling stage of injection molding process of thermoplastic composite reinforced with short fibers. We focused on analyzing the distribution of fiber’s orientation given by the variation of values of second-order orientation’s tensor in a rectangular geometry. The originality of our work is the introduction of a thermo-dependent law describing the behavior of material. This law is obtained experimentally using rheological measurements on online rheometer.

An experimental study of the thermorheological behavior of polypropylene (PP) reinforced with short glass fibers during the injection processing is described in this paper. This study was carried out using a proprietary rheometer which was designed and developed within our laboratory and is mounted on the injection machine. We have studied the variations of PP viscosity and elasticity, during isothermal flow, as a function of temperature, shear rate and glass fiber content. Furthermore we have studied the influence of the injection thermomechanical parameters during non-isothermal flowing and a pressure drop inside the feed channels and within a molding cavity of cylindrical cross section.

On presente une etude numerique des ecoulements dans les paliers hybrides. Ce type de probleme peut etre formule par l'equation de Reynolds, qui regit l'ecoulement dans le film mince, et deux equations de pertes de charges, aux niveaux des raccordements alveoles et au niveau des alimentations. Afin de determiner le champ de pression dans la totalite du palier (alveoles et film mince) une resolution numerique est faite par la combinaison de la methode des elements finis et de la methode du point fixe. L'avantage d'une telle approche se caracterise par sa validite pour tous les regimes de l'ecoulement (laminaire et turbulent) d'une part, et son adaptation a tous les types d'alimentation par capillaire ou diaphragme, d'autre part. On montre qu'on peut predire les performances de divers paliers en statique et en dynamique en quelques iterations.

The importance of polymer flow properties during processing has required the development of new on line measurement systems, able to work under rates encountered during industrial processes. This paper will describe a rheometer which is able to study the thermorheological behavior of polymers within industrial injection or extrusion machines. Its main feature is to work at high shear rates which are experimented during production processes; it is equipped with dies of different diameters and lengths, allowing shear rates between 102 to 107 s−1. Some results concerning viscosity and first normal stress differences are presented for high density polyethylene (HDPE), polypropylene (PP) and polypropylene/polyarylamide blends (PP/PA). The plot of viscosity and first normal difference against shear rate for these materials are not linear. Two non Newtonian regions and a third one similar to Newtonian behavior were observed in the wide range of shear rates up to 8.106 s−1.

To establish the constitutive equations for carbon/PMR-15 composites and to determine the contribution of the matrix to the mechanical response, an analysis of the behavior of the PMR-15 polyimide alone has been performed under thermomechanical loading conditions corresponding to military aeroengine applications. In particular, the creep behavior of the material has been studied for several combinations of stress (0.3 to 0.7 σr), temperature (250 to 300°C), and time (5 and 1300 h). The creep compliance has been modeled in the field where the behavior is linear, using the Burgers model, together with a retardation time distribution for the viscoelastic region. The viscoelastic behavior is described satisfactorily by the Kohlrausch function, and combined with the Maxwell relation, enables the creep compliance of PMR-15 polyimide to be modeled in the temperature range considered for short loading times. For long times at 250°C and 0.3 σr, the polymer undergoes slow plastic deformation, but nevertheless, conserves its overall viscoelastic properties. There is no equivalence between time and temperature. The master curve, constructed graphically on the basis of linear viscoelastic strains, short times, and a reference temperature of 250°C, deviates quite significantly from the experimental curve at longer times. In the latter case, the creep compliance curve can be correctly fitted to a simple power law. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1983–1991, 1998

Comprehension of the phenomena and conditions of the crosslinking of structural adhesives is invaluable in making performance structures. This crosslinking obviously depends on the formulation of the adhesive: i.e. the nature of the basic resin, of the crosslinking agent, of the various additives and of its composition. The work bears on the study of the crosslinking of epoxy resins in the presence of steels plated with different alloys, with a view to studying the behaviour of the adhesive/support system and investigating the effect on reactivity of the nature of the substrate's surface and the study of the mechanical behaviour of bonded assemblies under shearing. By determining the energy of activation, we have been able to highlight the catalytic effect of the supports on the crosslinking of the epoxy-diamine adhesive under consideration. We have demonstrated the greater efficiency of aluminium on adhesive-substrate interactions. Interaction seems possible between the hydroxyl group of the epo...

Our work deals with the viscoelastic behavior and the evolution of the morphology of polypropylene samples reinforced with short glass fibers and molded with an injection machine. The influences on polymer properties of the mold temperature, of the rate of fibers and of the embedding are studied. We determine the existence of typical relations between the microstructure, the thermomechanical parameters of the injection and the viscoelastic properties of the composite. All these results contribute to optimize the mechanical resistance of molded objects thanks to a better knowledge of the action of injection molding parameters.

La difficulte de mise en oeuvre de la resine PMR-15 sous forme de plaques massives pour realiser des eprouvettes n'a pas permis jusqu'alors de determiner ses proprietes mecaniques. Cette difficulte est contournee ici par la mise au point d'un procede specifique de fabrication en deux etapes. La caracterisation mecanique des produits obtenus a ete effectuee en chaque point d'un plan d'experiences construit a partir de conditions de moulage possibles. A l'aide des courbes de niveau, notamment celles de la contrainte a la rupture en traction, on definit les conditions optimales de cuisson. Les proprietes mecaniques determinees aux conditions de cuisson optimisees situent la PMR-15 a un niveau remarquable parmi les resines organiques.

This study deals with fibre orientation during injection moulding of polyarylamide and polypropylene/polyarylamide matrices reinforced with 30% of short glass fibres. The rheological behaviour of these two composites has been investigated with a capillary rheometer. The composites have also been injected into a rectangular plate cavity using two threshold gate geometries and several plate thicknesses, and the orientation of the fibres has been determined at given coordinates inside the plate. The effects of speed injection, moulding temperature and flow geometry on fibre orientation have been investigated.

Thermoplastic polymer alloys or composites present a structural anisotropy after injection molding. The evolution of such an anisotropy depends on the type and on the concentration of components and also on the thermodynamical conditions of processing. Thermomechanical properties of such materials evolute taking into account typical microstructures. In this paper, we study the influence of injection and mold temperatures and of injection speed on stress-strain, impact resistance and viscoelastic behaviour of 30% short glass fibers reinforced polypropylene/polyarylamide mixtures.

Polymers properties depend as well on resins and additives characteristics as on mol¬ding conditions and thermodynamical parameters. The study of polycarbonates shows that a tensile area more or less wide appears in the medium of a molded sample for specific molding temperatures on the walls, while a compressive area is identified at the same time close to the surface.These phenomenas have been studied and their incidence on particular mechancial properties of injected samples is related.

Resume Les facteurs thermodynamiques intervenant au cours de l'injection conduisent a une structure complexe de polymeres cristallins. Cette etude traite des relations entre la microstructure du polyoxymethylene injecte et certaines proprietes thermomecaniques. Des variations structurales dans l'echantillon par rapport au point d'injection ont ete mises en evidence, ce qui conduit a une anisotropie des caracteristiques mecaniques. Ainsi un modele de deformation en 2 etapes, microfissuration interlamellaire puis rotation-glissement des lamelles, permet d'expliquer l'influence de la microstructure sur le comportement en traction. Par ailleurs, la microstructure apparait plus dependante de la temperature du moule que d'autres parametres d'injection.

LES ASSEMBLAGES PAR COLLAGE NECESSITENT DES PRECAUTIONS OPERATOIRES TOUT AU LONG DE LEUR REALISATION. UNE ATTENTION PARTICULIERE DOIT ETRE PORTEE A L'ETAT DES SURFACES A COLLER, A LA GEOMETRIE DES JOINTS, A LA CONCEPTION DES PIECES A ASSEMBLER, AU CHOIX DE LA COLLE ET DE LA TECHNIQUE D'APPLICATION LIES AUX CONDITIONS D'EMPLOI. LA QUALITE D'EXECUTION DE CHACUNE DE CES ETAPES EST DETERMINANTE DANS L'EVALUATION DE LA VALEUR DU COLLAGE ET PAR LA MEME DES PROPRIETES DE L'ASSEMBLAGE. POUR S'ASSURER DE CETTE QUALITE ET REPONDRE AUX EXIGENCES DE L'EMPLOI UN GRAND NOMBRE DE TECHNIQUES DE CONTROLE ONT VU LE JOUR. CES CONTROLES PEUVENT ETRE CLASSES EN DEUX GRANDES CATEGORIES : LES CONTROLES DESTRUCTIFS ET LES CONTROLES NON DESTRUCTIFS. NOUS NOUS PROPOSONS D'EXAMINER ICI LES PRINCIPAUX TESTS SIGNIFICATIFS EFFECTUES SUR LES COLLAGES : TESTS DE PELAGE, CONTROLES SONORE ET ULTRASONORE, PAR MICRO-ONDES, RAYON X, CRISTAUX LIQUIDES, THERMOGRAPHIE INFRAROUGE, INTERFEROMETRIE HOLOGRAPHIQUE. (A).

This study deals with the compatibility of a poly(vinyl chloride) mixed separately with two industrial chlorinated poly(vinyl chlorides), denoted PVC/C1 and PVC/C2 (chlorine contents of 65.2 and 67.5%, respectively). The technique of mixing, examined for different compositions, is the main parameter for the compatibility of the resins. The mixtures were prepared either with a Brabender plastograph, with a milling cylinder at 190°C (the mixture being fluid), or by sintering at a temperature between 180 and 200°C under pressure. We determined the complex components of the elasticity modulus as a function of temperature (from 50 to 170°C at a frequency of 110 Hz) for each mixture, using a Rheovibron viscoelastometer. The study of the structure of the mixtures, based on the variation of the tangent of the loss modulus, allows us to say that the compatibility of polymers depends on the chlorine contents in chlorinated PVC; thus, at 65.2% the chlorinated polymer seems to be compatible with PVC, but at ...

Bi-injection molding generally requires two independent injection device systems to introduce molten polymers into the mold cavity.Both the tickness and orientation of the two materials in the finished molded product are dependent on the viscosities of the polymers as well as the rheological properties.This paper deals with a new, easy, simple, inexpensive bi-injection technology capable of producing specific structures according to expected properties while varying skin thickness to the desired level, both with or without fillers.

Resume Les differents modes de transformation et les parametres variables de la mise en oeuvre influent de facon considerable sur la structure des polymeres semi-cristallins. Le comportement mecanique de ces materiaux est en relation etroite avec l'importance relative des differents domaines structuraux. La modification eventuelle des parametres de mise en oeuvre est donc susceptible d'entrainer des consequences tres importantes a l'occasion de l'utilisation, tant en ce qui concerne les proprietes que le comportement a long terme des pieces fabriquees. Dans le moulage par injection, la temperature de l'empreinte intervient a cet egard de facon preponderante.

The study of a new spherically symmetrical apparatus to measure heat conductivity of particular liquids under transient heat transfer conditions is proposed. Three experimental investigations on paraffin oil, cyclohexanon, and macromolecular solution are presented.