In this research, a novel method of CVI + RMI 3DN C/SiC torque tube preparation has been researched. CVI + RMI 3DN C/SiC flat panel was evaluated by Archimedes drainage method for density and open porosity, SEM for morphological characterization, XRD for phase composition characterization, and chemical method for composition mass and volume content. It has an average density of 2.19 g cm⁻³, and open porosity of 10%. The computed chemical composition method findings are undoubtedly in line with the fiber design volume percentage of 30%. Tensile and shear mechanical tests on 3DN C/SiC standard sample were investigated, with good performance. The average tensile and shear strength was 141.64 MPa and 86.24 MPa respectively. 3DN C/SiC torque tubes were prepared by the same process, and the torsional mechanical tests were carried out. According to the mechanical parameters of the flat panel 3DN C/SiC sample, the mechanical properties of stress distribution and shear stress-strain curves for the torque tube are predicted by using the finite element simulation method, which is in good agreement with the test results. The test and simulation error of the maximum shear strength is only about 2%.

To overcome the inherent limitations of the ceramic matrix composite (CMC) process and increase the torque capacity of CMC torque tubes, this study investigated the failure causes of 2D woven chemical vapor infiltration (CVI) C/SiC and SiC/SiC combined CMC torque tubes. The CT test was used to describe the non-homogeneous density distribution of the CMC torque tubes. Using the Archimedes drainage method to evaluate density and porosity, we simulated the stress distribution and failure strength of CMC torque tubes using an FEM model. Fixtures suitable for universal material testing apparatuses were used for CMC torque tube torsional tests. The stress-strain curves showed that two distinct fiber types of CMC torque tubes displayed different torsional tendencies, and we examined the main causes of failure. The SiC fiber in the CMC torque tube increased maximum shear stress and modulus. Additionally, the strength of the SiC/SiC torque tube, rather than the interface between the C/SiC and SiC/SiC torque tubes, was the primary cause of combined CMC torque tube failure.