Mechanical and Thermal Properties of Silicon Carbide Composites with Chopped Si-Al-C Fiber Addition

The fabrication conditions of dense silicon carbide (SiC) composites containing chopped Tyrann (R) Si-Al-C (SA) fiber were examined in this work; SiC compacts containing SA fiber (mean lengths: 214, 394 and 706 mu m) were hot-pressed at 1800 degrees C for 30 min under a pressure of 31 MPa in Ar atmosphere. The fracture toughness of SiC composites with 40 mass% of SA fiber addition (sintering aid: 5 mol% Al4C3) increased from 2.8 up to 4.7 MPa.m(1/2) as the fiber length increased from 214 to 706 gm. The enhanced fracture toughness of the SiC composites was attributed to the lowering of fiber orientation angle (i.e., the angle between the fiber length and direction perpendicular to the hot-pressing direction) to 5 degrees with increasing fiber length. The fracture toughness of SiC composites could be further enhanced through the incorporation of SA fibers with a carbon interface (thickness: 100 nm) into the SiC matrix. The fracture toughness of SiC composite containing 40 mass% of these fibers attained 6.0 MPa.m(1/2). The thermal conductivity of SiC composites increased with fiber length from 30.5 W.m(-1).K-1 to 45.5 W.m(-1).K-1; with no significant influence being noted for the case of fibers with a carbon interface.