Effect of fiber heat treatment on microstructure and mechanical properties of 2.5D T700 carbon fiber reinforced SiC composites

T700 carbon fibers were heat treated at 1300 degrees C and 1600 degrees C to investigate the effect on microstructure of pyrolytic carbon (PyC) interphase and mechanical properties of 2.5D T700 carbon fiber reinforced SiC (2.5D C-f/SiC) composites, and the untreated carbon fiber acts as a comparison. The flexural strength was measured using three-point bending test and the fracture toughness was evaluated by a single-edge notched beam test. Results show that heat treatment at 1300 degrees C leads to highest mechanical properties of 2.5D C-f/SiC composites, with the flexural strength in warp direction of 248.6 +/- 12.3 MPa, the flexural strength in weft direction of 421.6 +/- 15.1 MPa, and the fracture toughness of 18.7 +/- 1.7 MPa . m(1/2). Nevertheless, both the unheated and heat treatment at 1600 degrees C result in a decrease in mechanical properties. The microstructural investigations revealed that the bonding strength between the carbon fiber and PyC is best when the heat treatment of carbon fiber at 1300 degrees C.