A Brief Review of Microwave Testing of Stratified Composite Structures: A Comparison between Plane Wave and Near Field Approaches


Stratified composite structures are increasingly being used in many critical applications. These composites are commonly manufactured from an army of dielectric or insulating materials. Depending on their thickness, layer structure or inhomogeneity, standard nondestructive testing (NDT) techniques may not always be able to effectively test these stratified structures for disband, delamination or coating thickness variation. On the other hand, microwave signals can penetrate inside of dielectric materials and interact with their inner structure, rendering microwave NDT techniques effective candidates for testing these structures. Microwave signals are also coherent, allowing for both phase and magnitude measurement. There are two basic approaches when using microwave NDT methods for testing stratified composite structures: namely, the plane wave (far field) approach and the near field approach. Each of these approaches possess certain advantages and drawbacks. This paper gives a succinct review of these two approaches and presents the results of a limited set of comparisons between the sensitivity of these two approaches when detecting coating thickness, coating thickness variation, debonding and delamination in conductor backed structures.


Electrical and Computer Engineering

Keywords and Phrases

Coatings; Composites; Delamination; Disband; Microwaves; Polymers; Thermal Barrier Coatings; Composite Testing And Evaluation

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version


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© 2002 American Society for Nondestructive Testing, Inc., All rights reserved.

Publication Date

01 Feb 2002

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