18 Novembre – Thesis defense - Edouard Marin
09 h30 Amphi LCTS - Pessac
Mechanical behavior of oxide/oxide CMC for aircraft structures.
Oxide/Oxide composites exhibit an interesting mechanical behaviour at high temperature. Hence, they are a of growing interest for new generation aircraft engines, allowing a higher working temperature while maintaining a low density. These two advantages would provide for decreasing fuel consumption and CO2 emission reduction. However, the fine understanding and the prediction of their mechanical behaviour in singular zones is still discussed. This knowledge is mandatory to design robust structural parts.
A study and comparison of two materials is proposed: a woven oxide/oxide composite, and a new generation laminate oxide/oxide composite made of unidirectional plies. The study is organized into two major parts, namely i) an experimental analysis and ii) a numerical analysis by multi-scale damage modelling. For the experimental part, multi-instrumented tensile tests are performed to identify and characterize the damages mechanisms. Then a micro-meso multi-scale damage model based on continuum damage mechanics is proposed, to meet two main objectives: i) enhance the understanding offered by the experimental analysis and ii) study the influence of process factors on the mechanical behaviour of the materials. The meso-model parameters are identified by virtual tests at micro-scale. This strategy allows a good prediction of the mechanical behaviour regardless of the considered laminate, and to study the effect of matrix porosity due to partial sintering. Effects of stress concentrations is eventually studied through tensile test on notched coupons. The use of experimental and numerical analysis offers the possibility to study the development of damage at the edge of notches. The two studied materials exhibit an interesting notch sensitivity, thanks to stress redistribution generated by matrix porosity.