Mechanical, dielectric and microwave absorption properties of SiO_2f/SiC_f/PI composites

Structural radar absorbing material attracts increasing attention as an important part of microwave absorbing material. In this study, fiber cloths reinforced polyimide (PI) matrix composites consisting of different proportion of quartz glass fiber (SiO_2f) and silicon carbide fiber (SiC_f) cloth were designed and prepared by adjusting the proportion. The morphology, mechanical, dielectric properties and electrical conductivity of the composites were thoroughly studied in X band (8.2-12.4 GHz). The results showed that the position of SiC_f cloth in the composite had little effect on the dielectric properties of the composite. Under the action of load, the fracture of composites containing different contents of SiC_f cloth showed different fracture modes. As the content of SiC_f cloth increased in the composite material, both the real and imaginary parts of complex permittivity showed an increasing trend. The electrical conductivity of the composites also increased gradually with content of SiC_f cloth rise. The reflectivity of the composites was calculated according to transmission line theory. Variation of fiber cloth composition in this study offered a new strategy to simultaneously improve the mechanical and microwave absorbing properties of PI-based structural absorbing materials.