Simulation des polymères par un modèle de comportement d'Hyperélasto-Visco-Hystérésis

L'objectif de cette étude est de mettre en place une méthode d'identification rapide des paramètres matériaux d'un modèle de comportement original, appelé modèle d' Hyperélasto-Visco-Hystérésis (HVH) sur un matériau polypropylène copolymère (PP) et d'étudier son comportement mécanique vis-à-vis de la vitesse de déformation. Des essais de traction quasi-statiques simples, cyclique et de relaxation ont été menés pour une vitesse de déformation de 8.10-3 s-1. Ensuite, des essais de traction rapides pour des vitesses de déformation de 8.10-2 s-1 à 200 s-1 ont été réalisés sur une machine servo-hydraulique. Ces résultats expérimentaux ont permis de déterminer les paramètres matériaux du modèle de comportement HVH. Tout d'abord les paramètres sont identifiés sur un essai de charge-décharge interrompu avec des phases de relaxation. Ensuite, les paramètres visqueux sont identifiés grâce aux essais de traction à différentes vitesses de déformation. Les résultats obtenus montrent que le modèle de comportement est capable de représenter le comportement en traction simple pour différentes vitesses de déformation, ainsi que le comportement en chargement cyclique et en relaxation

Elaboration and mechanical characterization of a polymer filled with Alfa fibers

International audienceThe objective of this work is to characterize the mechanical behaviour of a copolymer polypropylene (PPC7712) filled with Alfa fiber. First, elaboration method of the polypropylene/Alfa composite is presented. The concentration of fibers in the polypropylene matrix is of 15% in mass. In order to improve the adhesion fiber/matrix, fibers were chemically treated by an alkaline treatment. Its main objective is to remove a certain amount of lignin, wax and oils covering the external surface of the fibers. Next, the mechanical behaviour of these composites blend has been analysed. Monotonic tensile tests, cyclic loading/unloading) and tensile tests interrupted by relaxation steps were performed. These results allow us to determine the influence of reinforced fibers on the mechanical behaviour of polypropylene

identification of a behavior model of elastohysteresis for a polypropylène

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A mechanical analysis of a polypropylene copolymer reinforced by alfa fibers

International audienceThe main purpose of this work consists to characterize the mechanical performance of a copolymer polypropylene filled with Alfa fibers. The Alfa is the Arab name of the esparto grass or "stippa tenacissima" plant. The polypropylene used is a commercial grade, named PPC7712, already studied in static and dynamic tensile tests. In the first part of this study the elaboration of the polypropylene reinforced with these natural fibers was presented along with a microscopic analysis that showed us a good homogeneous distribution of natural fibers on the polypropylene matrix. The second part of this work present the analyses of the mechanical behavior of these composites blend. Contrary to classical research on polymer materials dedicated only to monotonic tensile tests, cyclic loading-unloading tests and relaxation tests are performed on the virgin and filled polypropylene material. Reinforcement by these natural fibers shows clearly an impact in the improvement of mechanical properties of this composite

High speed tensile test on the propylene

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New poly(p-phenylenevinylene) derivatives containing isosorbide unit in the side-chain

New conjugated PPV derivatives containing the chiral isosorbide group (P1-3) have been synthesized via the Gilch reaction. The polymers are optically active, soluble in common organic solvents and show good film-forming abilities. High number-average molecular weights were determined by size exclusion chromatography (SEC) (16•103–21•103 g•mol–1). The molecular structures of the polymers were confirmed by nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopies. Thermogravimetric analysis of the polymers showed good thermal stability up to 320°C. The optical properties of these π-conjugated materials were investigated by UV-vis absorption and photoluminescence (PL) spectroscopies. The polymers show a yellow fluorescence in dilute solution, and an orange emission is observed in thin films. The introduction of the polar isosorbide groups improved the PL intensity, and quantum yields between 50 and 73% were obtained. The HOMO-LUMO energy levels were estimated by cyclic voltammetry, and the electrochemical gaps were 1.81, 1.83 and 2.48 eV for P1, P2 and P3, respectively. Single-layer diode devices were fabricated and show relatively low turn-on voltages between 3.1 and 3.4 V