On Damage Degree and Evolution of Mechanical and Electromagnetic Properties for SiC f /Si 3 N 4 Composites in Rain Erosion Process

ABSTRACT This study comprehensively investigates the damage evolution and property degradation of SiC f /Si 3 N 4 composites subjected to high‐speed waterjet impacts simulating rain erosion. The composites are fabricated by CVI using SiC fiber fabric preform with BN interface and Si 3 N 4 matrix. A single‐jet device generates stable waterjets (≈350 m/s, ≈4.9 mm diameter) to induce controlled erosion damage. Results demonstrate a staged progression of erosion damage: initial localized fiber bundle fracture and matrix cracking (0%–25% depth) is followed by pit widening via water‐wedging and delamination (25%–75% depth), culminating in penetration with a stabilized damage area (>75% depth). Tensile strength decreases by 47.5% after full penetration, with AE analysis indicating a transition from synergistic fiber‐matrix failure to a fiber‐dominated quasi‐brittle fracture mechanism due to interfacial weakening and matrix damage. Conversely, electromagnetic analysis shows that the erosion‐induced damage, including pits, cracks, and increased porosity, improved impedance matching. This leads to a significant enhancement in wave‐absorbing performance, with the minimum reflection loss decreasing from −5.96 dB for undamaged material to below −7 dB for fully eroded specimen across the X‐band. This work elucidates the dual influences of rain erosion on the mechanical and electromagnetic functionality of SiC f /Si 3 N 4 composites, providing critical insights for aerospace applications.)