Perforation-tolerant phase-gradient metastructure stabilizes broadband microwave absorption via scattering redistribution

Abstract

Perforation is generally considered a worst-case failure mode for radar-absorbing structures because it removes lossy volume and amplifies edge-induced specular echoes. Here we show that, with phase-gradient scattering engineering, perforation can instead be leveraged as a controllable scattering-redistribution-and-loss element. A laminated metastructure that integrates a magnetic impedance-matching layer with a carbon-based multiple-reflection layer achieves broadband absorption (2–18 GHz) in the pristine state. Remarkably, although perforation increases the reflection amplitude locally, the phase gradient between adjacent subcells is largely preserved, which steers backward scattering away from the specular direction and stabilizes the global absorption/backscattering signature. The metastructure maintains effective absorption over 3–18 GHz under both periodic-array and randomly distributed perforation modes up to a 40% perforated area fraction. An inverted trend further emerges for a single central perforation: within a moderate damage window (hole radius ∼ 10 mm), the monostatic RCS is reduced relative to the pristine state, whereas larger holes eventually degrade as expected. Full-wave analyses indicate that pore-induced multiple scattering and edge-localized power dissipation compensate for missing absorber volume, explaining the counterintuitive damage-enhanced response. These results reframe perforation from an unavoidable liability into a practical design knob for damage-aware absorbing skins.