b'Probabilistic Failure Criterion of SiC/SiC CompositesUnder Multi-Axial LoadingPrincipal Investigator: Jia-Liang LeTeam Members/ Collaborators: Joseph F. Labuz, Takaaki Koyanagi, Chen Hu, Anna GorgogianniAn integratedO wing to its excellenttime-dependent probabilistic mechanical propertiesfailure of SiC/SiC cladding. In the and stability under highexperimental investigation, the PLS experimental andtemperature and neutron irradiationis determined through the examina-analytical framework isconditions, SiC/SiC composites havetion of stress-strain response, the developed for reliabilityemerged as a promising material foracoustic emission measurement, analysis of SiC/SiClight water reactors (LWRs) in theas well as the X-ray computed composite claddingsdevelopment of accident-toleranttomography. The theoretical under multiaxial loading. fuel (ATF) systems. Structural integ- framework is derived by combining rity and retention of hermeticity arethe finite weakest-link statistical two crucial requirements for SiC/SiCmodel and the subcritical damage claddings during normal operations,growth model. This theoretical and both of them are closely relatedmodel captures the time-dependent to the proportional limit stress (PLS)failure mechanism of the material, of the material. Understanding thewhich has a major consequence for behavior of SiC/SiC compositespredicting the lifetime distribution under multi-axial stress states andof the cladding. Meanwhile, the developing a probabilistic approachmodel also predicts that the failure for evaluating the structural vulner- statistics of the cladding depend ability are of paramount importancestrongly on the cladding length.for reliability-based analysis andThe results of the multiaxial design of SiC/SiC composite clad- experiments reveal the level of dings. So far, there has been verystatistical variation of the PLS of limited effort towards experimentalSiC/SiC materials under different and analytical investigations ofstress states. The theoretical model probabilistic failure of SiC/SiC clad- provides a robust analytical tool for dings. This critical knowledge gapextrapolation of small-scale labora-motivates this research. tory test results to the behavior of Project Description: full-scale claddings. These findings The proposed research is to developlay down a scientific foundation for a probabilistic failure criterion forthe development of reliability-based SiC/SiC composites under multi- design of SiC/SiC fuel claddings, axial loading, and to incorporate thewhich will play an essential role in criterion into reliability analysis ofimproving the structural safety and the structural integrity of SiC/SiCintegrity of LWRs.fuel cladding. The research consists of two parts: 1) experimentalAccomplishments: investigation of multiaxial failureThe overarching goal of this behavior of SiC/SiC composites,research is to develop a probabilistic and 2) theoretical modeling offailure model for SiC/SiC composites66 2022|AFC ACCOMPLISHMENTS'