Mechanical and electromagnetic shielding properties of carbon fiber reinforced silicon carbide matrix composites

Carbon fiber reinforced SiC matrix composites (C_f/SiC) were fabricated through chemical vapor infiltration. Effects of SiC content on the mechanical and electromagnetic properties of the as-prepared materials were studied systematically. The high volume fraction of SiC matrix is beneficial to the transfer of load to carbon fiber. With the increase of SiC content from 21.5 to 42.2 vol.%, the total porosity decreases from 38.5 to 17.8 vol.%, the flexural strength and fracture toughness of C_f/SiC increase from 38 ± 4 to 375 ± 10 MPa and from 6.2 ± 0.7 to 21 ± 0.3 MPa m^1/2. The electromagnetic interference shielding effectiveness of as-prepared C_f/SiC decreases from 43 ± 1.4 to 31 ± 1.1 dB over the frequency range of 8.2-12.4 GHz with the increase of SiC content. The decease of electromagnetic interference shielding effectiveness is mainly attributed to the decline of absorption loss. With the increase of SiC content, the electrical conductivity of C_f/SiC diminishes, leading to the conspicuous drop of the conductive loss, which plays the key role in lowering the absorption loss of electromagnetic waves.