Missions

Context :
Ceramic Matrix Composites are materials with very high mechanical and thermal performance whose use is currently experiencing strong growth, thanks to several key applications: aircraft braking and propulsion, space propulsion and atmospheric re-entry, heat exchange at very high temperatures in heavy industry and power generation. The design of structures incorporating CMCs requires detailed knowledge of their mechanical and thermal behavior at high temperature and its evolution over time under the effect of mechanical, thermal and chemical loads. However, obtaining this information in a usable form for engineers requires performing numerous mechanical tests under variable conditions of temperature, oxidizing/corrosive atmosphere and mechanical stresses, with a major effort on in-situ diagnostics and measurements.

Objectives :
Obtaining a methodological, experimental and theoretical framework sufficiently complete to follow the high-temperature deformations on the surface of a heterogeneous material and to produce the data required for the establishment of laws of anisotropic damageable behavior under varied conditions of solicitation, and to establish these laws.

Activités

Flowchart :
1 – Gathering information on the microstructural and mechanical characterizations of the initial materials: non-oxide ceramic matrix composites of all types
2 – Getting started with monitoring the deformations of a material by digital image correlation (DIC) during hot mechanical tests
3 – Design of an assembly of complex high-temperature mechanical stresses, mainly introducing shear, but also 3-point bending. The evolution of the geometry of the specimen in addition to the directions of stress will be an experimental parameter to be considered to obtain this state of stress.
4 – Familiarization with methods for identifying fields of the FEMU or "virtual fields" type
5 – Determination of one or more test configurations guaranteeing optimal "identifiability" of the behavior model, in particular in the presence of noisy kinematic data.
6 – Validation of the method for monitoring hot deformations by DIC and description of the limits of the method according to: the temperature, the gaseous environment, the geometry of the specimen and the level/type of mechanical stress.
Means :
Tensile and/or shear and bending mechanical tests at room temperature and high temperatures
Heating stages for the specimen during mechanical testing
CAD and FE calculation software for assembly design
Digital image correlation (DIC) with extraction of virtual fields, for identification of damage fields (FEMU or "virtual fields")

Compétences

Strong skills in Mechanics of Materials : experimental aspects, numerical modeling by FE methods (ABAQUS preferred)

Contexte de travail

LCTS is a joint lab of CNRS, Bordeaux University, CEA and Safran, located on the Bordeaux Campus. It has 34 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 33 permanent staff members, plus some 20 PhD candidates and 6 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

None