Radar Cross-Section Reduction of the Nozzle of an Airborne Platform Using Lightweight Auxetic Metamaterials

Abstract

The nozzle of an aircraft is a major source of radar scattering from the rear aspect of the aircraft, which undergoes higher operational temperatures. In order to reduce the radar scattering of these nozzles, high temperature radar absorbing materials (RAM) are essential. The thickness of these RAM typically increases to attain RCS reduction at lower frequencies, which subsequently leads to a higher weight of the structure. Therefore, this research study investigates the weight advantages of a star auxetic (SA) lattice made up of barium titanate to reduce the RCS of aircraft exhaust nozzles in the frequency range of 8-18 GHz. Modelling of SA with a complicated aircraft structure may lead to complexities in terms of Computer Aided Design and electromagnetic modelling and higher computational time for solving the electromagnetic problem using exact solvers. In order to simplify the computational problem, a homogenization and modified transfer matrix method is used to generate the RL performance. The RL from the proposed in-house tools is also compared with the Floquet port analysis. The RL performance obtained from the proposed method is also validated against experimental data. Comparative analyses are performed between SA and solid pure block (PB) barium titanate samples over 32761 SA and PB thickness combinations. Results show that selected SA samples with the same thickness achieve weight saving of approximately 60%, with 20dB lower RL than PB. The median RCS of the nozzle rear aspect also indicates that the SA-based barium titanate has an advantage in terms of weight penalty with similar or better RCS performance. The study demonstrates that auxetic metamaterials will be a multifunctional, lightweight, thermally stable, and radar absorbent structure for high temperature aircraft applications.