Zicheng Liu

Electromagnetic modeling of a periodic array of fibers embedded in a panel with multiple fibers missing

Our goal is to detect defects in composite materials composed by multi-layer planar plates with a periodic set of circular cylindrical fibers embedded within each layer. As a starter, the work presented is electromagnetic (EM) modeling and imaging of missing fibers in a fiber array standing in air. The multiple scattering method is utilized to analyze the electromagnetic behavior, and the corresponding imaging model is established directly from Lippman-Schwinger integral formulation. With the imaging model, standard MUltiple SIgnal Classification (MUSIC), and the proposed joint sparsity which borrows the idea from sparsity theory, are applied to retrieve the locations of missing fibers. Various numerical results are provided to illustrate availability and accuracy of the modeling and imaging.

Electromagnetic retrieval of missing fibers in periodic fibered laminates via sparsity concepts

Electromagnetic modeling and imaging of fibered laminates with some fibers missing is investigated, this extending to similarly organized photonic crystals. Parallel circular cylinders are periodically set in a homogeneous layer (matrix) sandwiched between two homogeneous half-spaces. Absent fibers destroy the periodicity. An auxiliary periodic structure (supercell) provides a subsidiary model considered using method tailored to standard periodic structures involving the Floquet theorem to decompose the fields. Imaging approaches from the Lippman-Schwinger integral field formulation as one-shot MUltiple SIgnal Classification (MUSIC) with pointwise scatterers assumptions and an iterative, sparsity-constrained solution are developed. Numerical simulations illustrate the direct model and imaging.

Fast Full-Wave Analysis of Damaged Periodic Fiber-Reinforced Laminates

A computationally efficient modeling approach to analyze transverse magnetic and transverse electric electromagnetic scattering from periodic fiber-reinforced laminates is introduced, when they suffer from missing, shrunk/expanded, displaced fibers, and inclusions. Such damages inside the initially periodic structure (the fibers as organized in a given matrix) are seen as undamaged zones with fictitious line sources properly set inside them, and the field results as a summation of responses to the exterior source and equivalent ones. Then, methods for periodic structures can readily be used. Various numerical results are proposed which are evidencing the interest of this approach.

Electromagnetic Modeling of Damaged Single-Layer Fiber-Reinforced Laminates

Computational modeling of a composite laminate made of a homogeneous planar slab wherein circular cylindrical fibers are periodically embedded is carried out when various damages affect the structure and destroy periodicity. Methods based on the Floquet theorem are inapplicable in direct manner. Supercell methodology yields a fictitious periodic structure, so as the electromagnetic field solution everywhere in space can be accurately modeled, provided that the supercell is large enough. Damages include missing, displaced, shrinked and/or expanded fibers, and cylindrical homogeneous inclusions. Plane-wave and line-source illuminations are accounted for in both TE and TM polarizations. Since often a prerequisite to imaging of damages, Green’s functions are considered in detail and computed with the array scanning method. A set of simulations is proposed, with comparison with a standard finite-element approach, and modeling accuracy and efficiency are discussed.

Electromagnetic near-field imaging of missing fibers in periodic fiber-reinforced laminates

Summary form only given. Much work has been and is being carried out about the electromagnetic behavior of planar laminates (and in parallel, due to similarities of organization, of some particular photonic crystals) which are involving within each layer a periodic array of commonly orientated fibers, as it is underlined in wherein many references on the topic can also be found, both in electromagnetics (and photonics) and elasticity.