Multiscale Modeling of Electromagnetic Radiation Transport

Abstract

The transport of electromagnetic radiation is a critical factor in determining many of the advanced features of novel materials, composites, and coatings systems. The radiation interaction with a material's surface, as well as its transport and interaction within the material, both combine to produce the overall electromagnetic signature of that object, which is the root cause of the color and appearance of these materials. Historically, approaches to light scattering behavior prediction focus on either the surface interactions or the bulk interactions, and the models most used today are valid only for certain compatible size and length scales of radiation. As next generation materials become more advanced, and increasingly have formulation components that reside on the nanoscale, a robust, rigorous, yet highly general approach to electromagnetic signature prediction is required. A hybrid, multiscale approach to the computational prediction of light scattering by coatings and composite materials is presented here, where ray tracing and geometric optics formalism tracks individual photons as they enter the material of interest, and finite element solutions to the Maxwell equations are used to generate the radiation interaction result of nanoscale inclusions embedded within the bulk of the material. The approach presented here is highly general in nature; scattering inclusions may be pigments, fibers, nanoparticles, air voids, or heterogeneous phase components. The multiscale approach enables investigation of the electromagnetic signature at various length scales, and predicts spectral reflectance, directional reflectance, and color, among other properties, of various multicomponent systems.