MICROWAVE IMAGING OF THICK COMPOSITE PANELS WITH DEFECTS

The results of an experimental study investigating the use of microwav es to inspect the presence of defects in thick composite structures ar e presented. Specially fabricated thick glass reinforced polymer compo site 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 wave -guide aperture is used to create images of the sample. These images i ndicate the ability of microwaves for detecting and locating defects a nd voids of different sizes and shapes in such thick composites. For o ptimal detection, the influence of standoff distance between the senso r and the panels is also studied. Results indicate that the proper cho ice of standoff distance enhances paw detection capability.