Damage evolution and failure mechanism of heterogeneous cladding tube under internal pressure: Experimental study and numerical modeling

Refractory metal-SiC_f/SiC heterogeneous composites provide a promising approach to ensuring the hermeticity of nuclear-grade SiC_f/SiC composites. However, their underlying failure mechanisms affecting their performance remain unclear. In this study, we used a combination of expansion plug testing and finite element modeling to systematically investigate the damage evolution process and failure mechanisms of Mo-SiC_f/SiC heterogeneous cladding. The established theoretical model effectively predicts the damage failure process and mechanical properties of heterogeneous composite cladding, showing good agreement with experimental results. Results indicate that the heterogeneous cladding exhibits a three-stage damage evolution characteristic: initial elastic deformation transitions into nonlinear behavior via matrix cracking, subsequent Mo layer fracturing activates unstable crack propagation, and structural failure ultimately manifests as localized damage in the SiC_f/SiC layer with preserved overall structural integrity. The gradient damage evolution reveals the synergistic effect of the heterogeneous cladding system, where the Mo layer not only bears hoop stress but also ensures the hermeticity, while the SiC_f/SiC layer provides structural support, effectively delaying catastrophic failure. This study offers key theoretical guidance for the design of accident-tolerant fuel cladding and provides essential insights for enhancing its mechanical performance.