Roll-to-Roll In-Line Implementation of Microwave Free-Space Non-Destructive Evaluation of Conductive Composite Thin Layer Materials

Grigorios Koutsoukis,Ivan Alic,Kamel Haddadi,Antonios Vavouliotis,Ferry Kienberger

doi:10.3390/app11010378

Abstract

A free-space microwave nondestructive testing and evaluation module is developed for the low-power, non-ionizing, contactless, and real-time characterization of doped composite thin-film materials in an industrial context. The instrumentation proposed is built up with a handled vector network analyzer interfaced with corrugated horn antennas to measure the near-field complex reflection S11 of planar prepreg composite materials in a roll-to-roll in-line production line. Dedicated modeling and calibrations routines are developed to extract the microwave conductivity from the measured microwave signal. Practical extraction of the radiofrequency (RF) conductivity of thin film prepreg composite materials doped with nano-powders is exemplary shown at the test frequency of 10 GHz.

Highlights

Microwave characterization techniques for the measurement of dielectric and conductive properties of materials have been widely described in the literature [1,2]
The general set-up consists of a pair of directive antennas associated to a vector network analyzer (VNA) to measure the free-space S-parameters of planar materials positioned in the trajectory of the radiated beam assuming far-field conditions [5,6]
From the calibrated microwave signals in the material reference planes, the complex permittivity can be determined after modelling of reflection at the air—material interface and the propagation in the material

Summary

Introduction

Microwave characterization techniques for the measurement of dielectric and conductive properties of materials have been widely described in the literature [1,2]. From the calibrated microwave signals in the material reference planes, the complex permittivity can be determined after modelling of reflection at the air—material interface and the propagation in the material. The accuracy in the extraction of the complex permittivity depends on the hardware resources and on the mathematical modeling adopted to express the measured S-parameters as a function of the geometry and the physical properties of the material under investigation. Most of the works reported in the literature are related to the development of free-space techniques assuming a transverse electromagnetic mode (TEM)

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Methods

Conclusion