Microstructure and Mechanical Properties of Unidirectional, Laminated C(f)/SiC Composites with α-Al(2)O(3) Nanoparticles as Filler

The effects of an α-Al(2)O(3) 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-Al(2)O(3) nanoparticles were added to the carbon fiber bundles using a slurry impregnation method, and then the C(f)/SiC composite with an α-Al(2)O(3) nanoparticle filler (C(f)/SiC-Al(2)O(3)) was fabricated using a precursor infiltration and pyrolysis method. The microstructure of the C(f)/SiC-Al(2)O(3) composite showed chemical compatibility between the α-Al(2)O(3) and the pyrolysis SiC. The C(f)/SiC-Al(2)O(3) 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(f)/SiC-Al(2)O(3) composite was 11.7 MPa. The SiC-Al(2)O(3) 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-Al(2)O3 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-Al(2)O(3) 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.