Mechanical and electromagnetic shielding performance of carbon fiber reinforced multilayered (PyC-SiC)_n matrix composites

Carbon fiber reinforced multilayered pyrocarbon-silicon carbide ((PyC-SiC)_n) matrix (C/(PyC-SiC)_n) composites were prepared by means of layer-by-layer deposition of PyC and SiC via chemical vapor infiltration. Effects of the number of PyC-SiC sequences (n = 1, 2 and 4) on matrix microstructure, electrical conductivity, mechanical and electromagnetic interference (EMI) shielding performance of C/(PyC-SiC)_n composites were investigated. The results show that with increasing the number of sequences, flexural strength and fracture toughness of the composites increase from 121 ± 17 to 193 ± 18 MPa and from 3.0 ± 0.1 to 4.2 ± 0.3 MPa m^1/2, respectively. The enhanced mechanical properties of C/(PyC-SiC)_n composites are attributed to the increasing number of interfaces, supplying more channels for crack deflection and propagation, which is favorable to more fracture energy dissipation. The total shielding effectiveness (SE) of the composites increases from 34 to 42 dB in the frequency range of 8.2–12.4 GHz with the increase of PyC-SiC sequences number due to the increasing electrical conductivity and polarization of the multilayered matrix. The high EMI SE combined with low density and good mechanical properties of C/(PyC-SiC)_n composites exhibit great potential as lightweight and high-performance structural and functional materials.