Effect of graphene nanosheets and potassium sodium niobate on microwave absorbing and mechanical properties of quartz fiber/polyimide composites

In this work, mechanical and dielectric properties of quartz fiber/polyimide composites filled with graphene nanosheets and potassium sodium niobate were investigated. Compared with the composites without GNs and KNN, the incorporation of 2 wt% GNs and 30 wt% KNN enhanced the mechanical property, and the flexural strength was improved 34.6%. The complex permittivity of composites in the X band increased with increasing GNs and KNN content, respectively. For the single layer microwave absorbers, the optimum RL bandwidth below − 10 dB is 2.8 GHz of sample 5 with the thickness of 2.2 mm. The double-layer absorbers exhibit more excellent microwave absorption properties than those of their single-layer absorbers. For example, the absorption bandwidths below − 13 dB can be obtained in the whole measured frequency range with the matching layer thickness of 3.3 mm and the total composites thickness of 5 mm.