Understanding fiber preform effects on tensile strengths of SiC/SiC composites prepared by chemical vapor infiltration based on a unified fiber bundle bending view

SiC/SiC composites are internationally recognized as viable thermal structural materials. Grasping the strength and the complex failure mechanisms is fundamental to comprehend their mechanical behaviors. Three types of SiC fibers and four weaving architectures were employed to fabricate eight types of preform, and the SiC/SiC composites were prepared by the chemical vapor infiltration. The microstructures were analysed by Computed Tomography imaging combined with intelligent recognition, mainly the weaving architectures and pores. Cracks in multi-layered SiC matrix exhibit periodic characteristics during propagation, enabling the theoretical in-situ strength of the fiber bundle SiC/SiC units. An empirical strength formula was established, which considered factors such as fiber bending, fiber orientation, proportion of fibers in longitudinal direction, and porosity. The deviation of the predicted strength from the actual value ranged from 0.78 % to 29.51 %. A unified fiber bundle bending view to understanding fiber preform effects on tensile strengths of SiC/SiC was introduced.