Improving the electromagnetic wave absorption performance of Cf/SiC composites through post–processing strategies

Simultaneously achieving high electromagnetic wave absorption and excellent mechanical properties in composites with a carbon fibre–reinforced SiC matrix remains a pivotal challenge for advanced aerospace applications. This study presents a dual–modification post–processing strategy that combines a periodic wedge–shaped surface structure with a SiO 2 –B 2 O 3 –Li 2 O–SiC absorbing coating. The engineered surface structure reduced the mean reflection loss ( RL ) from –(0.12–0.14) to –(1.88–1.92) dB by deflecting incident waves, and the absorbing coating further reduced the RL to –(4.92–5.01) dB owing to impedance matching and dipole attenuation. The prepared composites exhibited good electromagnetic wave absorption performance at 800 °C, with a mean RL of –(6.49–7.07) dB. Furthermore, interfacial stress analysis showed that the wedge structures redistributed the tensile stress into higher shear stress and lower positive stress, which increased the bond strength from 3.1 to 7.4–7.9 MPa. This post–processing approach successfully addresses the competing requirements of broadband electromagnetic stealth, high temperature resistance, and high load–bearing capacity, and thereby establishes new design principles for multifunctional ceramic matrix composites in extreme operational environments.