Effect of fibre directionality on the microwave absorption properties of 3D braided SiCf/SiC composites

SiCf/SiC composites reinforced with three-dimensional (3D) four- and five-directional braided SiC fibre preforms were successfully prepared through precursor infiltration pyrolysis method. The microwave absorption and dielectric performances of the two-composites were compared and investigated in the X-band. The 3D five-directional braided SiCf/SiC composites exhibited superior microwave absorption abilities with a minimum reflection loss of - 16.1 dB at 8.2 GHz and an effective bandwidth of 1.5 GHz with a thickness of 5 mm which were larger than those of the 3D four-directional composites. The differences in these properties of the two composites were attributed to the presence of axial yarns in the 3D five-directional braided composites. The fibre placement in the preform significantly affected the dielectric and microwave absorption properties of the composites. Results suggested that 3D five-directional braided SiCf/SiC composites are promising high-performance microwave absorption materials.