Ceramic matrix composites (CMCs) are considered as promising materials to lighten the aerostructures while withstanding high temperatures. In this work, two-dimensional carbon fiber reinforced polymer derived ceramic composites are studied. The composites were fabricated through a polymer infiltration and pyrolysis (PIP) process. The different steps of the PIP process are examined in order to obtain the best mechanical properties and to find the optimal procedure of pyrolysis with the minimum number of cycles (cost reduction). The impact of the number of pyrolysis cycles, of the temperature of pyrolysis, and of the final state of the composite (pyrolysed or reinfiltrated with resin) on the mechanical behavior and on the microstructure are investigated. The composites are analyzed using tensile tests at room and high temperatures, preceded and followed by microstructural observations (scanning electron microscopy and X-ray microtomography). Moreover, in-situ tensile tests in SEM are performed in order to observe the fracture response of the composite, and acoustic emission (AE) is also used to understand the damage mechanisms. The polymer derived matrix is analyzed using thermal analysis of the resin (TGA, DIL) as well as X-ray diffraction (XRD). The effects of atmosphere (air, vacuum, argon) on the mechanical behavior and the associated damage mechanisms of the composite at high temperatures are also investigated.

Finite elements models are constructed with the observations made on the damage mechanisms and the results obtained with the tensile tests. These models describing the composite at a mesoscopic scale allow to understand and therefore predict the properties as well as the mechanical behavior of the material at a macroscopic scale.

The results show that by modifying the pyrolysis parameters, the evolution of the matrix is different. The conversion of the polymer precursor into the ceramic plays a key role in the properties of the composite. Playing on the pyrolysis conditions impacts the fiber/matrix interface and therefore the mechanical behavior and the fracture response. Higher temperatures of pyrolysis seem to weaken the composite and a more brittle fracture is obtained. However, in composites pyrolysed at a lower temperature, a humidity absorption is rapidly observed. The impact of humidity on the properties is investigated.