Dielectric Characterization of Electromagnetic Mixing Model Assisted Optimization Derived Heterogeneous Composites for Stealth Technology

Abstract

In this contribution, the numerical and experimental dielectric characterization of electromagnetic (EM) mixing model-assisted optimization-derived heterogeneous stealth composites was carried out. First, a shuffled frog leaping algorithm (SFLA) fused with the EM mixing model was introduced for the optimal design of the composite under certain constraints. Based on the optimal solutions provided by the analytical model, the heterogeneous composites, constituted multiwalled carbon nanotube (MWCNT) and titanium-di-oxide (TiO2), were developed and characterized. The frequency-dependent dielectric measurements of composites are executed in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${X}$ </tex-math></inline-formula> -band (i.e., 8.2–12.4 GHz) using a waveguide-based microwave measurement technique. At 8.2 GHz, the maximum components of measured complex dielectric permittivity (i.e., <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon _{r}^{\prime }$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon _{r}^{\prime \prime }$ </tex-math></inline-formula> ) are 16.2 and 6, respectively. The dielectric loss tangent (tan <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta _{\varepsilon }$ </tex-math></inline-formula> ) of the composite has a maximum value of 0.3 in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${X}$ </tex-math></inline-formula> -band. The measured outcomes are compared afterward with the Maxwell Garnett (MG) effective medium model. The Bruggeman (BG) effective medium theory and Landau–Lifshitz–Looyenga (LLL) formulation are included for validation of the adopted MG model. The measured dielectric permittivity and effective medium responses strongly agree with each other. Further, the effect of the quarter-wavelength thickness ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> /4), and normalized impedance are studied to better understand the composite’s EM behavior. The effect of different inclusions (i.e., spherical, cylindrical, disks, and ellipsoidal) on the dielectric properties was also studied. The composite with cylindrical inclusions provided the best dielectric and stealth response. The measured and theoretical findings are in strong correlation and reflect the potential of the proposed model in the realization of efficient stealth composites.