Effect of infiltration time on microstructure and mechanical properties of C/C-SiC composites

By using reactive melt infiltration process, three kinds of C/C-SiC composites were prepared in different infiltration time. Weight gain rate, bulk density, fracture toughness and three-point flexural strength of the C/C-SiC composites were respectively tested, phase composition of the composites analyzed, and microstructure of the composites observed. The results show that there exist mainly two kinds of SiC particles in the C/C-SiC composites, i.e. nano-scale SiC particles and micro-scale SiC particles; with the increase of infiltration time, both volume density and mass fraction of SiC increase, but flexural strength decreases. When infiltration time is extended from 0.5 h to 5 h, density can increase from 2.16 g·cm^-3 to 2.21 g·cm^-3, and mass fraction of SiC increases from 21.54% to 31.72%, but flexural strength decreases from 133 MPa to 86 MPa. All the composites behave like non-brittle fracture similar to metal material with the fracture strain about 1.3% and fracture toughness within 9-10 MPa·m^1/2.