Distant Damage-Assessment Method for Multilayer Composite Systems Using Electromagnetic Waves

Abstract

In this paper, a damage assessment method for remotely inspecting the near-surface condition of multilayer composite systems is proposed. The method utilizes far-field steady-state electromagnetic waves reflected from the surface of multilayer composite systems and generates the in-depth profile of the inspected composite systems using inverse synthetic aperture radar (ISAR) imaging technique. Spatial imagery of the system can be reconstructed with the structural and geometric features of the multilayer system. These features are revealed by discrete scatterers in the imagery. Reconstructed imagery can be used for detecting construction defects and structural damages in the near-surface region of the system. The theoretical background of the method is described, followed by experimental measurements on glass-fiber-reinforced polymer (GFRP)-confined concrete cylinders with an artificial defect as an example of multilayer composite systems. Continuous waves in the frequency range of 8 to 12 GHz were used. The imaging results show that the proposed method can reveal the location and size of the embedded defect in the GFRP-concrete composite system, indicating the potential use of the method as a basis for distant radar/microwave nondestructive testing/evaluation techniques in civil engineering.