Lightweight MXene-Modified Aramid Fiber-Reinforced Silica Composites as Radar Stealth Armor at Elevated Temperature

Owing to the high specific strength and excellent impact resistance, aramid fiber (AF)-reinforced composites are widely considered as promising lightweight structural materials for next-generation unmanned aerial vehicles (UAVs). However, their performance at elevated temperatures is severely constrained by the thermal instability of polymer matrix. Herein, we demonstrate a novel aramid fiber-reinforced ceramic composite with a SiO₂ matrix as a thermally resistant radar stealth armor. To prevent fiber degradation during processing, the cold sintering process is employed to achieve densification of the SiO₂ matrix at merely 180 °C using Na₂SiO₃ as a transient liquid. Moreover, MXene modification of AF is introduced as an interphase to simultaneously enhance the interfacial shear strength and capability of microwave attenuation. By optimizing sintering conditions, the composite reinforced with a double layer of MXene-modified AF fabric exhibits a flexural strength of 166 MPa at room temperature and remains  stable up to 300 °C. Furthermore, the synergistic impact resistance from the ceramic matrix and AF fabric demonstrates excellent low-velocity ballistic shielding performance in the composite. Thanks to the capacitor-like structure and enhanced conduction loss of MXene interphase with increasing temperature, the composite realizes effective absorption bandwidth coverage throughout the X-band from room temperature to 300 °C. Therefore, this work proposes an energy-saving strategy for the development of heat-resistant, mechanically robust and microwave-absorbing composites for UAVs.