Title

Experimental Study of Thermo-Mechanical Behavior of SiC Composite Tubing under High Temperature Gradient using Solid Surrogate

Document Type

Article

Subject Area(s)

Mechanical Engineering, Nuclear Materials Engineering

Abstract

Nuclear grade silicon carbide fiber (SiCf) reinforced silicon carbide matrix (SiCm) composite is a promising candidate material for accident tolerance fuel (ATF) cladding. A major challenge is ensuring the mechanical robustness of the ceramic cladding under accident conditions. In this work the high temperature mechanical response of a SiCf–SiCm composite tubing is studied using a novel thermo-mechanical test method. A solid surrogate tube is placed within and bonded to the SiCf–SiCm sample tube using a ceramic adhesive. The bonded tube pair is heated from the center using a ceramic glower. During testing, the outer surface temperature of the SiC sample tube rises up to 1274 K, and a steep temperature gradient develops through the thickness of the tube pair. Due to CTE mismatch and the temperature gradient, the solid surrogate tube induces high tensile stress in the SiC sample. During testing, 3D digital image correlation (DIC) method is used to map the strains on the outer surface of the SiC-composite, and acoustic emissions (AE) are monitored to detect the onset and progress of material damage. The thermo-mechanical behavior of SiC-composite sample is compared with that of monolithic SiC samples. Finite element models are developed to estimate stress–strain distribution within the tube assembly. Model predicted surface strain matches the measured surface strain using the DIC method. AE activities indicated a progressive damage process for SiCf–SiCm composite samples. For the composites tested in this study, the threshold mechanical hoop strain for matrix micro-cracking to initiate in SiCf–SiCm sample is found to be ∼300 microstrain.

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