Mechanical property of 2.5 dimensional silicon carbide fiber reinforced silicon carbide composites

Silicon carbide fiber reinforced silicon carbide (SiC_f/SiC) composites were fabricated with a pyrocarbon interface layer between porous 2.5-dimensional SiC fiber preforms and SiC matrix deposited by the low pressure chemical vapor infiltration method. The effects of the interface layer thickness and matrix fabrication conditions on the mechanical properties of composites were investigated. The results show that a pyrocarbon inter face layer 0.1 m thick makes the flexural strength of composites increase by 104.2% from 144 to 294 MPa, and the fracture of the composite is in a non-catastrophic mode. But when the interface layer thickness is increased further to about 0.16 m the reinforcement effectiveness of the fiber decreases, and this causes the composite to have bad fracture performance. When the deposition temperature of the matrix is decreased from 1050°C to 950°C, the flexural strength of the composite increases by -45% from 188 MPa to 274 MPa. The porosity of composites increases and the SiC texture changes from rhomboid to spherical when the deposition pressure for SiC matrix fabrication is increased from 8 kPa to 16 kPa. Due to the fine SiC matrix, the strength of the composite increases slightly though the porosity is a little higher.