Free space microwave measurement for detecting corrosion under a thin paint of aluminium panel
This paper presents a free space microwave measurement methods which are non-destructive and noncontact to determine the corrosion under a thin paint on aluminium panel. For free space microwave measurements techniques, the measured parameters are reflection coefficients S11, transmission coefficients S21, dielectric constants, loss factors, and complex permittivity as a function of frequencies. This paper is focusing on metal backed method in order to detect corrosion under thin paint on Aluminium panel. The metal backed method will measure the free space reflection coefficients, S11 only. In order to obtain smaller errors of dielectric constant, it is required that the sample thickness to be close to odd multiples of quarter wavelength. The results of the complex permittivity of the samples were calculated from measured reflection coefficient S11 at frequency range of 8 GHz-12 GHz.
One-Port Methods for Complex Permittivity Measurement. Short Review
The fast-growing field of different applications for dielectric material requires of development new types of such kinds of material with a wide range of characteristics and different aggregate states. One of the most important parts of developing new material is a verification procedure of its electrodynamical characteristics, which gives us the possibility to compare measured values with calculated ones. For measurement material properties nowadays use a lot of different methods for the complex permittivity extraction in the wide frequency range, but all of these methods can be divided into two big groups – one-port and two-port methods. In this article, one-port methods for complex permittivity measurement were reviewed, such as open-ended coaxial probe (OCP), short circuit probe (SCP), coplanar probe (CP), and free space (FP) measurements. The area of implementation of the most popular one-port methods and realization features are described in the article. The positive and negative sides of each of the presented methods are considered.
Comparison of electrical physical and mechanical properties of textile composites using microwave nondestructive evaluation
Composites are expensive and destructive test methods are normally applied to determine their physical and mechanical properties. For textile composites, a nondestructive test (NDT) could save time and save cost if the physical properties such as moisture content, weave architecture, void content and fiber volume fraction can be deduced from electrical properties. Also, there would be savings if mechanical properties such as tensile stress and elastic modulus could be determined by NDT methods. In this research, microwave NDT (MNDT) techniques such as measurement of complex permittivities are used for correlation with physical and mechanical properties. For textile composites made from E-glass, Kevlar and carbon fiber, we have measured reflection coefficients, transmission coefficients and dielectric properties using a free-space microwave measurement system. Epoxy has been used as a resin. Experimental results are reported for dielectric constants and loss tangents of textile composites. Also, measured physical and mechanical properties of textile composites are reported.