Microwave Imaging System Development For Nondestructive Testing of Multilayer Structures Using Ultrawideband Noise Waveforms

Open Access
Author:
Navagato, Marc Dominic
Graduate Program:
Electrical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
June 01, 2018
Committee Members:
  • Ram Mohan Narayanan, Thesis Advisor
  • Julio Urbina, Committee Member
Keywords:
  • Non-destructive Testing
  • Noise Radar
  • Fiber-Reinforced Polymers
  • Multilayered Structures
  • System Development
  • Ultrawideband Waveforms
Abstract:
Many areas within the aerospace, automotive, civil, and consumer industries rely on the superior structural support and lightweight characteristics of composite materials. These composites are used heavily in military applications, where they are applied extensively to the interior and exteriors of various aircrafts, ships, and land vehicles. The problem, though, is that during the lifespan of these composite materials, they are subject to various hazards, such as impact damages and galvanic corrosion, which may cause significant physical damage and financial costs. Our research is conducted with the goal of identifying potential flaws within the internal layers of such composite materials using ultrawideband noise waveforms. Noise and pseudorandom noise waveforms foster many benefits over other traditional waveforms due to their excellent resolution capabilities, low-probability of intercept, and immunity to jamming characteristics. The system we have designed, which operates in the X-band frequency range (8.2-12.4 GHz), scans a sample within the near-field of a pair of aperture horn antennas and creates either a two-dimensional or three-dimensional reconstructed image of the sample under test. We have developed samples with traits similar to those of composites that have experienced real-world damages or defects. Our findings have allowed for the detection of air voids in glass-fiber reinforced polymer civil structures; detection of aluminum hydroxide (Al(OH)3)—a byproduct of galvanic corrosion—in hybrid composite materials; as well internal ply delaminations in unidirectional carbon-fiber reinforced polymers due to high mass, low velocity tool drops.