Description du sujet de thèse

Context of the study:
Carbon/Carbon (C/C/SiC) composites are superior materials for various applications in heavy industry and especially in aerospace, for example as reusable heat shields for space objects re-entering the atmosphere. They are manufactured in two major steps: (i) the manufacture of a C/C composite by repeated cycles of impregnation and pyrolysis of a resin in a preform made of carbon fibers, (ii) the impregnation of this material with molten silicon. As of now, these materials display lower performances than composites manufactured by the gas route, but are much more advantageous in terms of costs. The aim here is to contribute to improving them by sparingly using the gas route at crucial stages of the manufacturing process; to do this, it is also necessary to understand and characterize their mechanical behavior at room temperature and at room temperature.
These studies are being conducted within the framework of a German-French ANR-DFG project « IDeLSIC » in collaboration with the « Materials Resources Management » Institute of the Augsburg University (Bavaria).
Subject of the study:
This thesis work focuses on understanding the influence of the structure and architecture of the material on its mechanical behavior. For this, various samples will be studied, differing by the textile reinforcement and by the possible insertion of layers deposited by gas during manufacturing (mainly managed by German colleagues for the liquid route). The work will be structured around two axes: - Experimental characterization of the mechanical behavior by various tests on specimens and on elementary constituents or mini-composites; - Construction of a behavior model and identification thanks to the experimental results

Work program
• Mechanical tests at room and high temperature on various specimens (classic and models) using laboratory testing machines, with in-situ characterizations (acoustic emission, deformation fields, etc.)
• Morphological characterizations before and after testing
• Mechanical tests at room and high temperature in a testing machine under X-ray tomography with monitoring of the evolution by digital 3D image correlation.
• Thermomechanical analyses (TMA)
• Characterization tests of interfaces (push-in, push-out, etc.) and meso-constituents
• Construction of a multi-scale mechanical behavior model and identification of parameters based on experimental data
• Identification of material optimization pathways

Contexte de travail

LCTS is a joint lab of CNRS, Bordeaux University, CEA and Safran, located on the Bordeaux Campus. It has 36 years experience in basic science research on refractory composites. These high-performance materials are used in aviation, space, energy & industrial applications. LCTS is single research team working in project-oriented mode, in strong relation with its non-academic stakeholders. Currently it includes 34 permanent staff members, plus some 15 PhD candidates and 4 post-doc researchers.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.

Contraintes et risques

Work in a Restricted Access Area, subject to clearance from the Security and Defence Officer of CNRS.