Influence du procédé d'injection dans la simulation mécanique de thermoplastiques chargés en fibres de verre courtes

Titre du résumé joint : Modélisation du Comportement Cyclique d'un Thermoplastique Renforcé en Fibres de Verre CourtesNational audienceLes thermoplastiques renforcés en fibres de verre courtes présentent un comportement mécanique fortement non-linéaire lorsqu'ils sont soumis à des chargements cycliques, sous différentes conditions hygrothermiques. Une loi de comportement phénoménologique est proposée de façon à décrire différents mécanismes physiques, tells que la viscoplasticité, l'écrouissage ou l'adoucissement cyclique. La microstructure anisotrope, conséquence de la mise en forme par injection, est prise en compte dans le modèle par l'intermédiaire de tenseurs d'orientation

Multiaxial fatigue models for short glass fibre reinforced polyamide. Part II: Fatigue life estimation

WOSInternational audienceComponents made of short fibre reinforced thermoplastics are increasingly used in the automotive industry, and more frequently subjected to fatigue loadings during their service life. The determination of a predictive fatigue criterion is therefore a serious issue for the designers, and requires the knowledge of the local mechanical response. As the cyclic behaviour of polymeric material is reckoned to be highly nonlinear, even at room temperature, an accurate constitutive model is a preliminary step for confident fatigue design. Constitutive equations for the cyclic behaviour, developed and validated by the authors in Part I of this paper [Launay et al., Int J Fatigue, in press], are applied to the mechanical analysis of fatigue campaigns carried out by Klimkeit et al. and De Monte et al. on specimens made out of polyamide 66 reinforced with 35 wt.% of short glass fibres. Both studies are performed at room temperature, with material conditioned at the equilibrium with air containing 50% of relative humidity (RH50) or dry-as-moulded (DAM). Post-processing the cyclic response in steady-state allows the comparison of several fatigue criteria. The fatigue databases involve various loadings, including the study of multiaxiality and mean-stress effects on different microstructures. Among all physical quantities, the dissipated energy density per cycle ΔWdiss displays the best correlation with the fatigue life

Modelling the influence of temperature and relative humidity on the time-dependent mechanical behaviour of a short glass fibre reinforced polyamide

WOSInternational audiencePolymer matrix composites, and especially short glass fibre reinforced polyamides, are widely used in the automotive industry. Their application on structural components requires a confident mechanical design taking into account the sensitivity of the mechanical response to both temperature T and relative humidity H. In this paper, the constitutive model already developed by the authors (Launay et al., 2011) is applied to describe the non-linear time-dependent behaviour of a PA66-GF35 under various hygrothermal conditions. The extensive experimental database involves testing conditions under and above the glass transition temperature Tg. An equivalence principle between temperature and relative humidity is applied and validated, since the non-linear mechanical response is shown to depend only on the temperature gap T-Tg(H)

Multiaxial fatigue models for short glass fiber reinforced polyamide - Part I: Nonlinear anisotropic constitutive behavior for cyclic response

WOSInternational audienceComponents made of short glass fiber reinforced (SGFR) thermoplastics are increasingly used in the automotive industry, and more frequently subjected to fatigue loadings during their service life. The determination of a predictive fatigue criterion is therefore a serious issue for the designers, and requires the knowledge of the local mechanical response under a large range of environmental conditions (temperature and relative humidity). As the cyclic behavior of polymeric material is reckoned to be highly nonlinear, even at room temperature, an accurate constitutive model is a preliminary step for confident fatigue design. The injection molding process induces a complex fiber orientation distribution (FOD), which affects both the mechanical response and the fatigue life of SGFR thermoplastics. This paper presents an extension of the constitutive behavior proposed by the authors in a previous work [Launay et al., Int J Plasticity, 2011], in order to take into account the influence of the local FOD on overall anisotropic elastic and viscoplastic properties. The proposed model is written in a general 3D anisotropic framework, and is validated on tensile samples with various FOD and loading histories: monotonic tensions, creep and/or relaxation steps, cyclic loadings. In Part II of this paper [Launay et al., Int J Fatigue, 2012], this constitutive model will be applied to the simulation of different fatigue samples subjected to multiaxial cyclic loadings

Design and synthesis of triphenylphosphonium-porphyrin@xylan nanoparticles for anticancer photodynamic therapy

Most photosensitizers (PS) suffer from a lack of water solubility and from a low selectivity toward tumor cells. Delivery systems using nanoparticles make it possible to improve PS water solubility, and also tumor targeting via the enhanced permeability and retention (EPR) effect. Among the organelles, mitochondria are attractive target sites for drug-delivery strategies since they perform a variety of key cellular processes. Our study was aimed at synthesizing nanoparticles consisting of xylan-carrying porphyrins attached to a triphenylphosphonium moiety, in order to enhance the PDT effect through mitochondrial targeting. Hybrid nanoparticles were designed that consisted of a silica core coated with xylan substituted with porphyrin derivatives carrying a triphenylphosphonium moiety. These hybrid nanoparticles have been constructed, along with their counterparts devoid of silica core, taking into consideration the controversy surrounding the use of silica nanoparticles. Phototoxicity experiments, conducted against the HCT-116 and HT-29 colorectal cancer cell lines, showed that nanoparticles with porphyrins bearing a triphenylphosphonium moiety exhibited an enhanced photocytotoxic effect in comparison with free porphyrin or nanoparticles with porphyrins without the triphenylphosphonium moiety

Design and synthesis of triphenylphosphonium-porphyrin@xylan nanoparticles for anticancer photodynamic therapy

Most photosensitizers (PS) suffer from a lack of water solubility and from a low selectivity toward tumor cells. Delivery systems using nanoparticles make it possible to improve PS water solubility, and also tumor targeting via the enhanced permeability and retention (EPR) effect. Among the organelles, mitochondria are attractive target sites for drug-delivery strategies since they perform a variety of key cellular processes. Our study was aimed at synthesizing nanoparticles consisting of xylan-carrying porphyrins attached to a triphenylphosphonium moiety, in order to enhance the PDT effect through mitochondrial targeting. Hybrid nanoparticles were designed that consisted of a silica core coated with xylan substituted with porphyrin derivatives carrying a triphenylphosphonium moiety. These hybrid nanoparticles have been constructed, along with their counterparts devoid of silica core, taking into consideration the controversy surrounding the use of silica nanoparticles. Phototoxicity experiments, conducted against the HCT-116 and HT-29 colorectal cancer cell lines, showed that nanoparticles with porphyrins bearing a triphenylphosphonium moiety exhibited an enhanced photocytotoxic effect in comparison with free porphyrin or nanoparticles with porphyrins without the triphenylphosphonium moiety

Architecture et habitat social dans l’entre-deux-guerres : l’exemple des ensembles concertés d’habitation à bon marché de Poitiers

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La fabrication d’un morceau de ville à la fin du XIXe siècle : le cas du quartier Dunois à Orléans

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Les lotissements du quartier Madeleine de la fin du XIXe siècle aux années 1950

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Aménager et réglementer : planification et lotissements à Orléans des années 1920 aux années 1960

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