Transient Radar Method: A Novel Electromagnetic Illumination and Blind Analysis Technique for the Characterization of Multilayer Structures

Student thesis: Doctoral Thesis


In the last few decades the industrial usage of many new (multi-layered) composite materials such as Glass Reinforced Polymers (GRP), Carbon Reinforced Polymers (CRP), Textile Reinforced Cements (TRC), sandwich materials comprising foams, honeycombs) has been substantially increased as they offer novel combinations of material properties to advance the state-of-the-art in material engineering: lightweight, strength, chemical inertness, electrical properties, etc. The introduction of these novel composites in many different industries such as in construction engineering, energy transport, aircraft and automobile sector, however, require the development of novel non-destructive testing techniques as in many cases the traditional NDT (Non-Destructive Techniques) such ultrasound or thermography, are no longer sufficient at the level of precision, penetration depth, measurement speed, consumption of coolants, etc. This PhD thesis deals with a novel generic contact-free NDT, exploiting the propagation properties of electromagnetic waves, focusing on the 10 to 100 GHz band. The proposed technique, called transient radar method, is a fully blind method allowing to simultaneously extract geometrical information and dielectric properties from the multi-layer structure under study. The fundamental operation principles will be unraveled as well as the numerical simulation code and results will be discussed. These theoretical findings will be backed with experimental results. A first experimental study focusses on the electromagnetic propagation properties of a wide variety of composite materials in the 10 to 100 GHz spectral band. A second experimental study has been executed with a dedicated proof-of-concept TRM set-up, operating at 10 GHz. The different error sources, the random as well as the systematic ones, will be quantified. Appropriate compensation algorithms are developed. Finally, we discuss the fundamental limits of this novel electromagnetic measurement technique and the future development tracks.
Date of Award3 Mar 2017
Original languageEnglish
Awarding Institution
  • Vrije Universiteit Brussel
SupervisorJohan Stiens (Promotor)


  • novel non-destructive testing techniques
  • electromagnetic waves
  • transient radar method

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