In-situ observation of damage evolution in Mo-SiCf/SiC heterogeneous composite

Innovative metal-SiCf/SiC heterogeneous structure composites are promising accident tolerance fuel cladding materials for the Gen IV advanced reactors. The mechanical damage of these composites is a critical issue for their safe application. In this work, the damage process and mechanism of the Mo-SiCf/SiC cladding are revealed by combining In-situ C-ring test and Finite Element Analysis. The results show that the mirco-cracks originate from the pores in the outermost side of the SiCf/SiC layer, and propagate along the fiber bundles boundaries. At the same time, the "bamboo joint"-like damage occurs in the SiCf/SiC layer during C-ring test due to the periodic pore distribution. The fact that the formation of the main crack in SiCf/SiC layer prior to the fracture of Mo layer indicate the Mo-SiCf/SiC cladding can maintain the hermeticity and structure integrity until the sample fails completely. Moreover, the C-ring strength of the Mo-SiCf/SiC cladding is 360 MPa, which is much higher than 201 MPa of SiCf/SiC cladding. Overall, the Mo-SiCf/SiC cladding structure exhibits better crack growth resistance and higher strength compared to SiCf/SiC cladding. Meanwhile this work will provide technical support and theoretical basis for the structural design of cladding materials for advanced nuclear energy systems.