Mechanical and friction-wear properties of two C/C composites using pre-oxidized polyacrylonitrile fibers and carbon fibers as the reinforcements

Two preforms based on pre-oxidized polyacrylonitrile fibers (OPFs) and a Chinese version of T-300 carbon fibers (CFs) were densified to 1.7 g/cm(3) by chemical vapor infiltration. The microstructures and mechanical and friction-wear properties of the two C/C composites were investigated. Results indicate that both composites exhibit a pseudo -plastic fracture mode with similar bending strengths of 127 MPa for the CF C/C composite and 113 MPa for the OPF C/C composite. The interlaminar shear strength of the OPF C/C composite is 13.4 MPa, which is 30.26% higher than that (10.01 MPa) of the CF C/C composite. It is easier to obtain pyrocarbon with a rough lamellar structure for the OPF reinforcement than with the CF one. The OPF C/C composite always gives a more stable COF and lower wear rate than the CF-based one, regardless of the braking conditions used. When the brake pressure is 0.65 MPa and the braking speed is 20-25 m/s, the OPF C/C composite has excellent abrasive wear resistance with a coefficient of friction near 0.35 and a linear wear rate of 1.3-1.5 pim per braking procedure.