Multi-scale design and mechanical enhancement of SiCf/SiC composite cladding for accident-tolerant fuel

The development of high-performance accident-tolerant fuel SiC f /SiC composite cladding is critical for advancing fourth-generation nuclear reactor technology. However, the theoretical frameworks for designing the fiber braided structure of SiC f /SiC composite cladding remain underexplored. This study presents the design of an innovative multi-layer gradient braided SiC f /SiC composite cladding through parametric modeling and evaluates its performance using a multi-scale coupling approach. Results show that gradient braiding significantly enhances cladding strength and toughness. Compared to a uniform 45° braiding angle, gradient braiding increases tensile strength and ultimate tensile strain by 50 % and 30 %, respectively. Under internal pressure, a 60°/45°/30° gradient structure achieves the highest hoop tensile strength and strain. Additionally, the established multi-scale numerical model has been verified by existing experiments and successfully predicted the mechanical behavior of the SiC f /SiC composite cladding, including the identification of crack initiation and propagation paths. Furthermore, the mechanical behavior of the cladding was analyzed at both microscopic and macroscopic scales, offering valuable insights for improving and optimizing the stress distribution between SiC fibers and the SiC matrix.