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Theses

Comportement mécanique de composites oxydes : Relations procédé-microstructure-propriétés

Abstract : The aim of this thesis is the fine understanding on the influence of the microstructure on oxide-based ceramic matrix composites mechanical properties. These materials are good candidate for new generation of civil aircraft engines. The aim of this work is to establish a relationship between the microstructural defects generated by the manufacturing process and the mechanical behavior of the composite. These heterogeneities seem to influence the appearance and the propagation of damage mechanisms. This study is realized on three kinds of bi-dimensional oxide composites generated from three different manufacturing processes. These processes create three kinds of microstructure. Porosimetric and μ-tomographic analyses allow estimating the distribution of microstructural defects and establish typical microstructure of each oxide composite. Based on these preliminary analyses, mechanical behavior of each kind of oxide composites is studied through several representative scales. On the one hand, mechanical tensile tests are carried out in order to estimate the mechanical properties of the studied materials in the weaving plane. On the other hand, the implementation of in-situ mechanical tests allows the visualization of damage mechanisms appearance and propagation. These observations improve the understanding of the role of microstructural defects on the activation of damage mechanisms. Damage kinetics of each mechanical test are inspected through AE (Acoustic emission) analysis. This monitoring helps to link mechanical behavior with microstructural damage. In parallel with global AE analysis, AE clustering is achieved. These classifications are based on two kinds of AE sensor with different properties. Data fusion from the two sensors is accomplished. This technique allows more robust AE clustering. Cluster labelling is proposed thanks to damage mechanisms observed during in-situ mechanical tests. Damage scenarios are set up owing to macroscopic mechanical test, in-situ analysis and AE labelling. Thus, it is possible to establish the influence of each kind of microstructural defect on oxide-based CMCs mechanical behavior.
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https://tel.archives-ouvertes.fr/tel-02061776
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Submitted on : Friday, March 8, 2019 - 12:44:15 PM
Last modification on : Wednesday, September 16, 2020 - 4:10:47 AM
Long-term archiving on: : Monday, June 10, 2019 - 12:59:32 PM

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  • HAL Id : tel-02061776, version 1

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Nicolas Guel. Comportement mécanique de composites oxydes : Relations procédé-microstructure-propriétés. Matériaux. Université de Lyon, 2018. Français. ⟨NNT : 2018LYSEI104⟩. ⟨tel-02061776⟩

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