High toughness, 3D textile, SiC/SiC composites by chemical vapor infiltration

Three dimensional, textile, Hi-Nicalon, silicon carbide fiber-reinforced, silicon carbide composites with high toughness and reliability were fabricated by chemical vapor infiltration. The mechanical properties of the composite materials were investigated under bending, shear, and impact loading. The density of the composites was 2.5 g cm -³ after the three dimensional silicon carbide perform has been infiltrated for 30 h. The values of flexural strength were 860 MPa at room temperature and 1010 MPa at 1300°C in vacuum. Above the infiltration temperature, the failure behavior of the composites became brittle because of the strong interfacial bonding and the mis-match of thermal expansion coefficients between fiber and matrix. The obtained value of shear strength was 67.5 MPa. The composites exhibited excellent impact resistance and the value of dynamic fracture toughness, 36.0 kJ m-² was measured by Charpy impact tests.