Optimization of a Portable Microwave Interference Scanning System for Nondestructive Testing of Multi-layered Dielectric Materials

A portable microwave interference scanning system has been demonstrated to detect damage in composite ceramic armor test specimens including engineered features in specially fabricated surrogates. The system has been optimized for detection of identified features in sample specimens. The system has been optimized for portability and field application flexibility, including miniaturization and wireless interfacing of it components. Composite ceramic armor is employed in the form of plate inserts in garments and seats; in panels in vehicles, aircraft and vessels; and as an appliqué in armored vehicles. Effectiveness of ceramic armor can be degraded by defects present from production and by operational damage resulting from handling or impact with objects in the environment, other than projectiles. In normal use, ceramic armor is routinely exposed to the possibility of such damage. The microwave interference scanning technique detects and images internal cracks, internal laminar features such as disbonds and variations in material properties such as density. It requires access to only one surface, and no coupling medium. Other NDE methods, including through-transmission x-ray, x-ray Computed Tomography, and destructive examination, are used to verify defects and other detected anomalies. The development of this portable system will provide a suitable method for intheatre health monitoring of composite ceramic armor. The Wireless Hand Held Prototype system is shown in Figure 1. The correlation between the microwave interference scanning image scan of the artificially cracked tile (center) and a through-transmission x-ray image of the same tile (right) is shown in Figure 2. A photograph of the face of the damaged region of the armor panel is shown in Figure 2 on the left. The wide, light gray patterns with dark edges in the microwave image are interference patterns centered on the crack centerlines which are identified with red marker lines.