Effects of fiber contents on the mechanical and microwave absorbent properties of carbon fiber felt reinforced geopolymer composites

In this paper, phosphate-based geopolymer composites are studied and the effects of different carbon fiber felt contents (from 20 vol% to 40 vol%) on the phase composition, microstructure, mechanical properties and microwave absorbent properties from 2 GHz to 18 GHz frequency band of the composites were systematically investigated. The results indicate that with the increase in carbon fiber felt contents, flexural strength and Young's modulus of the composites gradually increased. The fracture mode of the composite changed from brittle failure to ductile failure with the presence of carbon fiber felt. It was mainly due to the micropore deformation as well as fibers pulling-out and the crack deflection, which consumed most fracture energy. However, microwave absorbent performance tended to increase at first and then decreased as the carbon fiber felt content ramping up. When the content of carbon fiber felt in the composite was 26.7 vol%, the composite showed the best microwave absorbent performance and the reflection loss reached to − 59.3 dB. It is mainly attributed to the Debye polarization of the carbon fibers and the interface polarization between fibers and the matrix.