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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.

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...

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.

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 ...

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.