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Contribution à l’étude du comportement mécanique d’un PPS/GF40 sous différents chargements avec prise en compte des effets de l’environnement de sollicitation : étude expérimentale et modélisation multi-échelle pour application au développement de pièces automobiles

Abstract : This thesis presents an experimental and theoretical study conducted on a PPS/GF40 and its matrix. Widely used for under-the-hood applications in the automotive industry, those materials are subjected to high temperatures and aging effects of cooling liquid. Therefore, the understanding of those phenomena is essential to design mechanical parts. Thus, an experimental campaign in the tensile mode has been carried out with different temperatures and glycol proportions in the cooling liquid, for monotonic and cyclic loadings on neat and reinforced PPS. The results of these tests allowed us to highlight some of the main physical phenomena occurring during these solicitations under tough hydro-thermal conditions. Taking into account this analysis, a visco-elasto-pseudo-viscoplastic model is proposed. Moreover, this model allows the consideration of the cooling liquid effects and its constituents by temperature/humidity equivalence. The accuracy of the model was confronted to an artificial intelligence based one, in order to study the maximal accuracy physically reachable. Finally, the evolution of the model parameters has been studied with the adjunction of short glass fibres and for specifics orientation distribution. Starting from the study of the mechanical behavior of the PPS matrix, an analytical homogenization was then performed. Differences between experimental and predicted plastic behaviors were highlighted. Finite element analyses considering inter-phase damage were done at different temperatures and for several fiber orientations so to explain differences arising between analytical approach and experimental results. This work allowed a study of the evolution of the impact of this damage on mechanical properties as a function of temperature and fiber orientation. This work led to highlight a weakening of the fiber/matrix interface for a liquid aged composite and to quantify the decrease of the interface properties. Finally, fatigue behavior of the composite is studied as a function of fiber orientation. The modeling parameters determined from the study of the monotonic behavior of the composite were taken into account to propose a prediction of the Wöhler curves as a function of temperature. The prediction of the Wöhler curves as a function of temperature being possible, a 1D model was then proposed in order to evaluate the increase of temperature due to self-heating phenomenon during fatigue loading, considering ageing consequences.
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https://hal.univ-lorraine.fr/tel-03176321
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Submitted on : Monday, March 22, 2021 - 11:56:15 AM
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  • HAL Id : tel-03176321, version 1

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Quentin Bourgogne. Contribution à l’étude du comportement mécanique d’un PPS/GF40 sous différents chargements avec prise en compte des effets de l’environnement de sollicitation : étude expérimentale et modélisation multi-échelle pour application au développement de pièces automobiles. Science des matériaux [cond-mat.mtrl-sci]. Université de Lorraine, 2020. Français. ⟨NNT : 2020LORR0181⟩. ⟨tel-03176321⟩

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