Radar-Absorbing Multilayer Structure Based on Conformally Networked CNT-GFRP and PMI Foam for RCS Reduction in Leading Edge Application

초록

This study presents a multilayer radar-absorbing structure (RAS) composed of conformally networked CNT-coated glass fabric (CNC-GF) and PMI foam for aircraft leading edge (LE) applications. The conformal CNT coating formed by a dipping-drying cycle created a continuous conductive network, yielding distinct electromagnetic properties compared to conventional prepregs with CNTs dispersed in the resin matrix. To determine optimal design parameters, the 99% absorption bandwidth (BW99%) was analyzed as a function of CNC-GF and PMI foam thickness, and three representative structures (L10, L16, L22) were selected by varying the number of foam layers. Comprehensive simulations of return loss (RL) and radar cross section (RCS) were performed to evaluate absorption and stealth performance. Results showed that BW99% increased up to 10 layers owing to impedance matching and multiple internal reflections, but decreased with further thickening as resonance conditions destabilized. L10 achieved the widest BW99% (90.4%) under flat-plate conditions, whereas L22 exhibited the highest RCS reduction (95.0%) in LE geometry due to enhanced multiple reflections and phase interference. Field distribution analyses confirmed that while RL was primarily governed by impedance matching and dielectric loss, RCS reduction was dominated by interference effects under curved conditions, especially in VV polarization. These findings highlight that RL and RCS do not necessarily correlate, and emphasize the necessity of integrated absorption-scattering analysis for the design of multilayer stealth structures.

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