Modeling of Shielding Composite Materials and Structures for Microwave Frequencies

Abstract

Abstract-Composites containing conducting inclusions are required in many engineering applications, especially, for the design of microwave shielding enclosures to ensure electromagnetic compatibility and electromagnetic immunity. Herein, multilayer shielding structures are studied, with both absorbing and reflecting composite layers. In this paper, fiber-filled composites are considered. For modeling absorbing composites with low concentration of conducting cylindrical inclusions (below the percolation threshold), the Maxwell Garnett theory is used. For reflecting layers, when concentration of inclusions is close to or above the percolation threshold, the McLachlan formulation is used. Frequency dependencies for an effective permittivity are approximated by the Debye curves using a curve-fitting procedure, in particular, a genetic algorithm.

Homogenized Permittivity of Composites With Aligned Cylindrical Inclusions for Causal Electromagnetic Simulations

“…However, reasonable values for σ are on the order of 10 3 − 10 4 S/m [51]. The other type of inclusions found in the literature is chloroprene rubber inclusions [53], and in this study this material is also considered in Cases 3, 4, and 6 as the host material [51]. Parameters for the other cases in the Table 1 are a combination of those mentioned herein.…”

“…It is known that conductivity of carbon fibers varies over a wide range; and carbon fibers may be manufactured with different dimensions (diameters and lengths). However, reasonable values for σ are on the order of 10 3 − 10 4 S/m [51]. The other type of inclusions found in the literature is chloroprene rubber inclusions [53], and in this study this material is also considered in Cases 3, 4, and 6 as the host material [51].…”

“…The Teflon (PTFE) material is usually employed as the base material (host matrix) for design of shields for microwave frequencies (100 MHz-10 GHz). This material [50] is almost non-dispersive in the frequency range of interest, and its loss factor can be neglected, thus the constant value ε s = 2.2 is employed [51]. Inclusions in the Cases 2 and 4 are made of Barium Titanate (BaTiO 3 ) [52].…”

Electromagnetic Shielding Features in Lightweight PVDF-Aluminum Based Nanocomposites

“…Several investigations were carried out for the estimation of shielding effectiveness and reflectivity of layered laminate structure made for combination of different materials. In this way, polymer-based carbon-filled composites [14], or a sandwich of conductive polymer between a conductor and microwave absorber (i.e., Ca-NiTi hexa ferrite, carbonyl-iron particles, barium ferrites, MnZn ferrite) [15] can be used for wideband microwave shielding structures. Other laminated shields are considered as the combination of several layers constructed using conductive polymer, i.e., polyacetylene and poly-p-phenylenebenzobis-thiazole (PBT), doped with iodine, and conducting materials like copper and aluminum [16].…”

Dielectric and Electromagnetic Behavior of Conductive Nanocomposites Polymers: PP/MWCNT Investigations for EMI Applications

“…Nonetheless, the request to reduce the weight and the cost of these "safety" structures requires the replacement of metal by novel materials like conducting polymers and composites. These composites may include metal insertions, carbon, chemical substances or other inserted components with good dielectric conductivity [3].…”