A numerical study of lateral compressive strength of 3D needle-punched C/C control rod guide tubes

[Background] C/C composite material is one of candidate materials for molten salt reactor control rod guide tubes due to its excellent mechanical properties at elevated temperature. [Purpose] This study aims to promote the application of C/C composite in molten salt reactors, and evaluate the ultimate load and damage process of 3D needle-punched C/C guide tubes. [Methods] First of all, the ultimate compressive load of a control rod guide tube was measured by a quasi-static lateral compression experiment. Then, a three-dimensional progressive damage model of the control rod guide tube was established on the base of Tsai-Wu strength tensor theory and considering the reduction of material stiffness during progressive damage of composite materials. Based on this model, a user subroutine was developed to predict its lateral compressive strength. Finally, the ultimate bearing capacity of guide pipes of different sizes was obtained by simulation, and the quasi-static lateral compression process was simulated and compared with the experimental results. [Results and Conclusions] The numerical results show that the damage model can predict the ultimate bearing capacity of control rod guide tube. Further calculations of guide tubes of different sizes show that the ultimate load is closely related to the radius and thickness of the control rod guide tube. (authors)