Abstract: Silicon carbide (SiC) composite cladding has emerged as a disruptive fuel cladding technology in advanced nuclear energy systems, owing to its high specific strength, remarkable neutron irradiation resistance, and excellent high-temperature oxidation resistance, demonstrating significant potential to replace conventional zirconium alloy cladding. However, the structural complexity of SiC composites hinders a comprehensive understanding of their mechanical failure behavior under service conditions, which in turn constrains the pace of technological iteration. Therefore, to deeply reveal the damage mechanism of SiC composite cladding, accurately predict its stress-corrosion cracking risk in extreme environments, and further accelerate its engineering application, systematic multi-scale mechanical damage studies are essential. This review focuses on the research methodologies employed in multi-scale mechanical damage investigation of nuclear-grade SiC composite cladding. It covers macroscopic and micro‑/nano‑mechanical testing, in‑situ monitoring and characterization techniques such as digital image correlation, X‑ray computed tomography, and acoustic emission, as well as in‑situ electron microscopy characterization and multi‑scale numerical simulation. Significant progress has been achieved in this field: macroscopic mechanical tests can effectively characterize the overall mechanical performance of SiC composite cladding; multiple in‑situ techniques enable multi‑dimensional tracking of damage evolution from surface to interior and from static to dynamic processes; micro‑/nano‑mechanical testing provides critical support for obtaining mechanical parameters of key micro‑constituents, including fibers, matrix, and interfaces; and multi‑scale numerical simulations have established a predictive framework that effectively correlates microscopic mechanisms with macroscopic responses. Finally, prospects for future development and remaining challenges in this research area are outlined.

Key words: nuclear SiC composite cladding, multi-scale mechanical testing, in-situ characterization, multi-scale numerical simulation, review