Intelligent phase transition of polyimide-based composite foam for dynamic radar/infrared stealth

Intelligent radar/infrared stealth materials exhibit the capacity to dynamically modulate their radar/infrared stealth performance under different environmental backgrounds, which is of critical importance in military applications. In this paper, a dynamically modulated radar/infrared stealth composite is integrated by combining polyimide (PI) foam in its bottom, PI foam/carbon nanotube (CNT)/anisotropic iron (Fe)/vanadium dioxide (VO₂) in its middle, and VO₂ coating on its top. The unique phase transition characteristic of VO₂ effectively promotes significant changes in the conductivity, emissivity, and electromagnetic parameters of the composite foam, thereby motivating the intelligent regulation of radar/infrared stealth performance. Consequently, the radar stealth performance of composite foam can be switched between -4.17 dB at 30 ^oC and -61.69 dB at 120 ^oC at a thickness of 2.36 mm. Moreover, the bottom-designed polyimide thermal barrier layer can effectively block thermal radiation, thereby contributing to reducing surface temperatures. Simultaneously, VO₂ coating on the surface exhibits lower infrared emissivity after phase transition. The synergistic effect of reduced surface temperature and infrared emissivity contributes to the realization of intelligent infrared stealth. The present work proposes a promising strategy for designing actively adjustable stealth materials to cope with multi-band military detection in complex operational scenarios.