Multiscale Interfacial Phenomena and Mechanical Response in Advanced SiCfiber/SiCmatrix Composites 6 views

As the demand for energy production continues to increase, more robust materials systems are urgently required that can enable technological advances in power generating applications. These materials must withstand harsh environments while exhibiting thermal stability, chemical inertness, and performance at temperature. Silicon carbide fiber reinforced silicon carbide matrix (SiCf/SiCm) ceramic matrix composites (CMCs) possess a wide suitability to meet various environmental and loading demands through tuning of geometry and properties. The complex nature of these composite materials presents many critical questions regarding the interfacial response of various constituents within the assembly of SiC CMCs at multiple length scales. This dissertation examines mechanical response of three different interfacial regimes: part- part assembly (macroscale), interlayer interaction (mesoscale), and fiber-interphase-matrix behavior (microscale). A suite of experimental and characterization techniques is employed to evaluate various critical interfacial and intrinsic properties in relation to full-scale tests of components and assemblies. Analytic modeling is provided throughout to elucidate the stress- strain state at the local region of interest and how this behavior influences failure at the global level. A SiC CMC contains a myriad of interwoven layer interactions from joining of SiC surfaces to individual layer interactions at the nanoscale of fiber interphases. Thus, it is critical to understand how the coordination of interfacial phenomena separates CMC behavior from that of traditional monolithic ceramics. Through this work, design considerations are revealed to tailor performance of SiC CMCs to meet the various performance demands within harsh environments. Furthermore, a constant thread is maintained that considers commercial viability and robust scaling methodology to separate this work from a purely esoteric discussion of thermal, chemical, and mechanical interplay within interfacial materials science. Key findings include (i) a method for improving the joining of SiC components with a thorough analysis of the thermomechanical mechanism of action, (ii) the contribution of an inner monolithic SiC layer on the failure response of multilayered SiC CMCs, and (iii) a mechanistic evaluation of the properties of the fiber-interphase-matrix system that cause discrete failure in CMCs. This dissertation uses the materials framework of advanced SiC/SiC CMC tubes for nuclear fuel cladding applications as the context to derive the insights and implications that will aid future development of CMCs for power generating applications.

PHD (Doctor of Philosophy)

silicon carbide; ceramic matrix composites; interfacial

English

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2026-04-09