Mechanical properties of 3D fiber reinforced C/SiC composites

High toughness and reliable three dimensional textile carbon fiber reinforc ed silicon carbide composites were fabricated by chemical vapor infiltratio n. Mechanical properties of the composite materials were investigated under bending, shear, and impact loading. The density of the composites was 2.0- 2.1 g cm(-3) after the three dimensional carbon preform was infiltrated for 30 h. The values of flexural strength were 441 MPa at room temperature, 45 0 MPa at 1300 degreesC, and 447 MPa at 1600 degreesC. At elevated temperatu res (1300 and 1600 degreesC), the failure behavior of the composites became some brittle because of the strong interfacial bonding caused by the mis-m atch of thermal expansion coefficients between fiber and matrix. The shear strength was 30.5 MPa. The fracture toughness and work of fracture were as high as 20.3 MPa m(1-2) and 12.0 kJ.m(-2), respectively. The composites exh ibited excellent uniformity of strength and the Weibull modulus, m, was 23. 3. The value of dynamic fracture toughness was 62 kJ.m(-2) measured by Char py impact tests. (C) 2001 Elsevier Science B.V. All rights reserved.