关键词: 2D SiC/SiC, 随机振动, 疲劳损伤, 等效应力, 拉伸性能

Abstract:

Under demanding service conditions, the operational requirements, namely high-temperature performance and structural weight reduction, in aero-engine hot section components continue to intensify. Silicon carbide fiber reinforced silicon carbide matrix (SiC/SiC) composites are widely recognized as exceptionally promising alternative materials owing to their outstanding high-temperature stability, substantially reduced density and superior corrosion resistance. However, in actual service environments, these composites inevitably experience complex vibrational loading spectra, which induce fatigue damage accumulation emerging as a critical limiting factor in their practical engineering implementation. In this study, 2D SiC/SiC plates were fabricated by chemical vapor infiltration. Specimens featuring bilateral arc-shaped notches were machined from the plates and subsequently subjected to narrow band random vibration fatigue tests under the first-order vibration mode. This experimental approach was undertaken specifically to investigate the progressive damage evolution process and the accompanying degradation patterns in tensile properties under vibrational fatigue loading. The experimental findings reveal that the normalized full time-domain characteristic curves of the 2D SiC/SiC plate structures exhibit progressive downward displacement while the applied equivalent stress amplitude increases. These curves concurrently manifest pronounced statistical dispersion throughout low-stress loading regime. Based on microstructural analyses, the damage evolution within the 2D SiC/SiC plate structure can be classified into three distinct and sequential stages: the initial matrix damage stage, the subsequent interface damage stage, and the final fiber damage stage. Quantitatively, the damage progression rate follows a distinct correlated three stage evolution—commencing with rapid progression, then transitioning to reduced propagation velocity, and lastly culminating in accelerated damage advancement. Residual tensile properties demonstrate that the tensile characteristics of the 2D SiC/SiC plate structure follow an exponential decline trend. At a resonance frequency reduction of 31.9%, the tensile strength, proportional limit stress, elastic modulus, and resilience modulus have degraded to 270.0 MPa, 64.1 MPa, 106.3 GPa, and 0.020 MJ/m³, respectively, all falling below 70% of the corresponding values in the as-fabricated pristine state. Subsequent analyses of the tensile fracture surface reveal matrix cracking and pronounced fiber wear as the dominant damage mechanisms responsible for the significant degradation observed in the tensile properties of the vibration fatigued composite structure. These findings provide a critical experimental basis for assessing the service reliability of 2D SiC/SiC plate structures under vibrational service conditions.

Key words: 2D SiC/SiC, random vibration, fatigue damage, equivalent stress, tensile property