Electromagnetic modeling of damaged fiber-reinforced laminates

Abstract

As a prerequisite to nondestructive testing of damaged fibered laminates, the Green's function, corresponding with an undamaged structure, and the electromagnetic fields associated with the damaged one are investigated herein. For the undamaged fibered laminate, benefiting from the periodicity of the fibers within each layer, the field solution follows the scattering-matrix-based method using the Floquet theorem. Yet, the periodicity is destroyed by the analytical source (for the Green's function) or by damages, and the Floquet theorem cannot be directly applied to compute the associated scattering matrices. The array scanning method is introduced to that effect. Inserting fictitious sources to get a quasi-periodic source array, the modeling approach for undamaged laminates can be used to compute the field with the source array, the integration of which cancels the effects of the fictitious sources and yields the Green's function. With the multipole method, field disturbances by damages, which include missing, displaced, shrunk, and expanded fibers and circular inclusions inside fibers, are accurately modeled by setting equivalent sources inside sound fibers, and the array scanning method applies. Modeling accuracy and efficiency of the approaches are illustrated by numerical simulations.