Electromagnetic Energy Localization and Characterization of Composites

This dissertation examines the electromagnetic (EM) properties of two component composites. These composites exhibit varying degrees of complexity, ranging from those containing single cube inclusions to those consisting of hundreds of irregularly shaped inclusions in a disordered arrangement. Specifically, time-domain EM modeling is used as a tool to calculate effective permittivity as well as EM localization behavior for these mixtures. For single inclusion mixtures with high permittivity contrast between the inclusion and the surrounding matrix material, strong deviation from established mixing theories is found. It is also shown that the orientation of the inclusion impacts the effective electrical permittivity of the composite. Electric fields are found to localize on the edges and corners of an irregular inclusion independent of simulation boundary conditions. Increasing the complexity of the studied mixtures, the EM properties are then analyzed for mixtures containing many irregularly- and regularly-shaped inclusion crystals. A strong correlation between effective permittivity and cross-sectional area is found for these mixtures. With hundreds of inclusion crystals (with either irregular or cube shapes), the change in inclusion shape causes negligible differences in effective permittivity. Electric energy density localizes on edges and corners of inclusions regardless of inclusion shape. A result not highlighted by single inclusion mixtures, for composites containing numerous inclusions significant increases in energy localization are observed as the EM signal travels through more inclusions. This increase in hotspot magnitude is observed for complex mixtures with hundreds of disordered irregularly shaped inclusion crystals. The same behavior is also observed for the much simpler scenario of a few dozen cube inclusions distributed within discrete parallel planes. As a result, a key conclusion from this work is that the study of hotspots does not require the use of geometrically complex structures with hundreds of irregular inclusions. Rather, much simpler arrangements of fewer and regularly shaped inclusions can be analyzed since they exhibit similar energy localization behavior.