Microstructure and Mechanical Properties of Unidirectional, Laminated C/SiC Composites with α-Al₂O₃ Nanoparticles as...

The effects of an α-Al₂O₃ nanoparticle filler in the SiC matrix on the mechanical properties and failure mechanism of the unidirectional, laminated carbon fiber-reinforced SiC composites were investigated in this work. First, α-Al₂O₃ nanoparticles were added to the carbon fiber bundles using a slurry impregnation method, and then the C/SiC composite with an α-Al₂O₃ nanoparticle filler (C/SiC-Al₂O₃) was fabricated using a precursor infiltration and pyrolysis method. The microstructure of the C/SiC-Al₂O₃ composite showed chemical compatibility between the α-Al₂O₃ and the pyrolysis SiC. The C/SiC-Al₂O₃ composite with a low porosity of ~6.67% achieved a good flexural strength of 629.3 MPa and a good fracture toughness of 25.2 MPa·m^1/2. The interlaminar shear strength of the C/SiC-Al₂O₃ composite was 11.7 MPa. The SiC-Al₂O₃ matrix also presented a considerable Young's modulus of 138.2 ± 8.66 GPa and hardness of 10.3 ± 1.03 GPa. Further analysis indicated that the good mechanical properties with the addition of an α-Al₂O3 filler were not only related to the dense matrix and the improvement of the mechanical properties of the matrix. They also originated from the thermal residual compressive stress in the SiC matrix close to the α-Al₂O₃ nanoparticles caused by the thermal expansion mismatch, which could reflect and close the cracks in the matrix. The findings of this study provide more methods for designing new composites exhibiting a good performance.