Microwave near-field and far-field imaging of composite plate with hat stiffeners

Abstract

Composite stiffened structures that are widely used in engineering inevitably produce various defects in manufacturing and service. In order to detect them, a microwave nondestructive testing platform is built in this paper, which simply combines near-field and far-field microwave scanning imaging. 0.4 mm metal hole, 0.5 mm and 1 mm inclusions and 0.1 mm thick debonding are detected by high resolution microwave near-field imaging. Internal poor resin infusions defects in 39 mm thick hat stiffener are detected by high penetration microwave far-field imaging. Far-field microwave images the shape and internal structure of stiffener by adjusting stand-off distance. Detection of the fiber wrinkling defects demonstrates the effectiveness of combining near-field and far-field imaging methods, saving 95% of the scan imaging time. Feature-based image stitching technique is adopted to obtain the full-size image of the large stiffened composite structure.