Effect of SiC/C preform densities on the mechanical and electromagnetic interference shielding properties of dual matrix SiC/C–SiC composites

SiC/C–SiC composites were fabricated via a chemical vapor infiltration (CVI) method using porous SiC/C composites as preform. The influences of the SiC/C preform densities on the mechanical, microstructure and electromagnetic interference shielding properties (EMI) of the SiC/C–SiC composites have been studied. Results show that the SiC/C–SiC composites densities increase with increasing the SiC/C preform densities. When the SiC/C preform density is 1.21 g/cm3, the flexural strength, shear strength and toughness of the corresponding SiC/C–SiC composite can reach 220 MPa, 20.98 MPa and 10.21 MPa m1/2, respectively. The surface reflection (SER) and the internal absorption (SEA) both increase with increasing the SiC/C preform densities. The enhancement of the EMI is mainly attributed to the formation of conductive networks by the continuous pyrolytic carbon (PyC) matrix and the surface reflection is the dominant shielding mechanism.