Modeling and analysis for the anisotropic irradiation swelling of porous SiC/SiC composites

Abstract

SiC/SiC composites are one of the promising engineering materials for nuclear applications. Anisotropic swelling deformations were observed in these materials during irradiation, and the underlying mechanisms should be deeply understood. In this study, a numerical simulation method is developed to predict the irradiation-induced deformations of the as-fabricated SiC/SiC composites. An emphasis is given to the generation of an RVE (Representative Volume Element) model with a pre-existing pore and the assumed residual stress field. Besides, the thermo-mechanical constitutive relations and stress update algorithms for the solid skeleton of porous SiC/SiC composites are developed with their irradiation effects considered comprehensively. Based on the homogenization theory, the calculation models to obtain the macroscopic swelling strains of porous SiC/SiC composites are developed. The good agreements between the predictions and the post-irradiation data of anisotropic swelling validate the effectiveness of the developed models and simulation methods. Research findings indicate that the irradiation creep deformations due to the existing residual stresses and high transient creep rate coefficients lead to the through-thickness size shrinkage of the pre-existing pores, which possibly becomes the dominant mechanism of the negative linear swelling of the SiC/SiC sample during the initial irradiation stage. The effects of the initial residual stress fields and the elastic constitutive relations on the anisotropic irradiation swelling behaviors are investigated. This study lays a foundation for the advanced manufacture of the SiC/SiC composites and the based multi-layer cladding tubes.