Numerical modeling and damage mechanism analysis of typical fiber orientations of unidirectional carbon fiber-reinforced silicon carbide

Carbon fiber-reinforced silicon carbide (C/SiC) composite materials are widely used in aerospace and rail transportation due to their high specific strength, thermal stability, and oxidation resistance. However, their anisotropic and brittle structure can easily lead to fiber fracture, matrix cracking, and interfacial debonding during grinding, severely affecting surface quality and service performance. To systematically elucidate the removal mechanisms under different fiber orientations, this study developed a three-dimensional grinding finite element model considering the three-phase synergistic interaction between carbon fibers, the SiC matrix, and the PyC interface. The material behavior was described using the Johnson–Holmquist II model, the VUMAT subroutine, and the Cohesive Surface method. Through C/SiC grinding simulations and experimental validation, the study concluded that the grinding force ranking is B > A > C, with direction B being the most challenging to process; When the grinding depth reaches 30 μm and the stress exceeds 10 MPa, cracks propagate along the SiC matrix and fiber gaps, leading to interface delamination; in subsurface damage, cracks in direction B reach a maximum depth of 25 μm and are prone to causing matrix brittle fracture; interface damage is most severe in direction B, extending to 50 μm below the surface layer. The results are highly consistent with experimental SEM images, validating the model's accuracy. This study achieved coupled modeling of micro-scale removal behavior and macro-scale grinding force response under different fiber orientations, providing theoretical support for optimizing low-damage processing techniques for high-performance C/SiC composite materials.