Electromagnetic analysis of heterogeneous woven fabric composite laminates
Date
2019
Authors
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Publisher
University of Delaware
Abstract
Defense and aerospace industries have been utilizing composite materials for a range of benefits for many decades. For example, composite materials have been shown to have a low thermal conductivity, high strength, low weight, and be corrosion resistant. More recently composites have been used for multifunctional applications that combine good mechanical properties with desirable electromagnetic (EM) properties. For example, some research groups have attempted the integration of RF subsystems (e.g., Frequency Selective Surfaces, Reflect Arrays, Planar Antenna Arrays) into a more complex composite structure. Integrating the EM behavior of the composite in the initial design phase would present an immense benefit to the composite manufacturers. This dissertation presents a methodology for quantifying the EM response of heterogeneous composite laminates. The design workflow can be seen as three step process: 1) determine the effective material properties of all the constituent materials within the composite fabric weave, 2) assign material properties to a repeating-unit-cell (RUC) geometric model which accurately represents the weave morphology, and 3) determine the scattering coefficients from the developed fabric. ☐ Step one requires knowledge of the EM properties of the constituent materials over a broad spectrum of frequencies. For low loss dielectric composite materials like glass, the effective properties are typically determined using effective media equations. However, for composites that include high conductivity materials like carbon, those previous models are potentially no longer accurate. This work demonstrates a method for calculating the effective material properties of an arbitrary multiphase material by using a semi-analytic boundary value technique which numerically determines all EM fields of an arbitrary collection of N-layered 2-D cylinders. These fields are used to define a single, effective, homogeneous isotropic cylinder whose bistatic scattering cross-section matches the cylinder collection. Step two will show the method for constructing a 3-D finite element model suitable for use in a computational EM (CEM) solver. Additionally, while it is not considered in this work, these geometries are appropriate for characterizing the mechanical performance of the composite laminate. In the present work, leveraging previously described geometries defining plain, 4-, 5-, and 8- harness satin weaves, a correspondence matrix (CM) is developed extending the geometries to the entire family of satin and twill fabric weaves. Step three will use these geometries to determine the EM scattering characteristics from high contrast woven fabrics with different weave architectures. The scattering coefficients are numerically determined using a commercially available CEM solver; however, the implementation of the geometries allows the parametric study of the composite weave architectures which could then be used in an optimization/sensitivity study. The result of this work is a methodology which includes computational models for predicting the broadband EM behavior of heterogeneous composite fabrics that include conductive or high contrast fiber tows.