HRTEM investigation of local damage mechanisms at fiber/matrix interface of SiC/SiC composites
Résumé
The behavior of fiber/matrix bonding leading to poor/fair damage tolerance of SiC/SiC composites was investigated through the observation of the local damage mechanisms in this interface region.SiCf/SiCm composites reinforced with last generation small diameter SiC fibers are promising candidates for thermomechanical applications in nuclear environments. The ability of these SiCf/SiCm composites to sustain damage is dictated by the fiber/matrix coupling mode, achieved through a pyrolytic carbon (PyC) interphase. In this study, opposite coupling behaviors were compared. Push-out tests were conducted on SiC/SiC composites. Indented fibers were extracted by FIB (Focused Ion Beam) and the microstructural organization of the carbon interface around a dislodge fiber were analyzed by HRTEM (High Resolution Transmission Electronic Microscopy).The experimental results have demonstrated the key role of the characteristics of SiC fibers surface and of its structure of carbon rich multi-layers on the macroscopic mechanical behavior of the SiC/SiC composite. It has also been proved that crack deflection occurred near the fiber/PyC region rather than near the matrix/PyC one. This technique is promising for the understanding and the improvement of the interfacial properties of the ceramic composite materials.
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