Microwave imaging of thick composite panels with defects

Abstract

The results of an experimental study investigating the use of microwaves to inspect the presence of defects in thick composite structures are presented. Specially fabricated thick glass reinforced polymer composite panels with several types of embedded defects are inspected using an open-ended rectangular waveguide sensor. A voltage related to the phase or magnitude of the effective reflection coefficient at the waveguide aperture is used to create images of the sample. These images indicate the ability of microwaves for detecting and locating defects and voids of different sizes and shapes in such thick composites. For optimal detection, the influence of standoff distance between the sensor and the panels is also studied. Results indicate that the proper choice of standoff distance enhances flaw detection capability.