ETD

• additive manufacturing
• C/C- SiC
• ceramic matrix composites
• damage tolerance
• fracture thoughness
• LSI
• thermal shock

Ceramic Matrix Composites (CMCs) are advanced structural materials designed to overcome the intrinsic brittleness of monolithic ceramics while retaining excellent thermal and chemical stability. Among them, C/C–SiC composites are particularly attractive for high-temperature and aerospace applications due to their low density, enhanced fracture toughness, and thermal shock resistance. The integration of additive manufacturing offers new opportunities for producing complex CMC architectures with controlled microstructural features.
This thesis investigates the damage tolerance of C/C–SiC composites fabricated through fused filament fabrication (FFF) of carbon-fiber-reinforced polyetheretherketone (CF-PEEK) filaments, followed by thermo-oxidative stabilization, pyrolysis, and liquid silicon infiltration (LSI). Damage tolerance is addressed at the material level within a fracture mechanics framework, focusing on the role of microstructure, manufacturing-induced anisotropy, and processing-related defects.
An experimental campaign is conducted to characterize mechanical and thermal behavior. Flexural testing and Single-Edge Notched Beam (SENB) tests are employed to evaluate stiffness, strength, and fracture toughness. Low Velocity Impact (LVI) tests are performed to investigate the impact response and failure mechanisms of the material; however, impact events led to complete specimen fracture, preventing post-impact residual testing. Thermal behavior is analyzed through measurements of thermal diffusivity, coefficient of thermal expansion, and thermal shock resistance. Damage and fracture mechanisms are examined by optical microscopy.
The results provide insight into the impact sensitivity and damage tolerance limits of additively manufactured C/C–SiC composites, contributing to the understanding of processing–structure–property relationships in advanced ceramic matrix composites.