Ali Foudazi | Missouri University of Science and Technology (original) (raw)

Papers by Ali Foudazi

The non-uniform distribution of steel fibers in fiber-reinforced cement-based mortars (FRCMs) can... more The non-uniform distribution of steel fibers in fiber-reinforced cement-based mortars (FRCMs) can lead to heterogeneous properties of hardened material with direct impact on mechanical properties. Among various nondestructive testing techniques, the active microwave thermography (AMT) has shown good potential for inspection of cement-based materials. AMT utilizes combination of microwave energy to generate controlled and localized heating and uses commercially-available infrared cameras to capture surface thermal images in real-time. Utilizing AMT, four FRCM samples made with different steel fiber volumes ranging from 0 to 3 % were investigated to evaluate the feasibility of this method for detecting and quantifying fiber distribution. Full-wave coupled electromagnetic-thermal numerical modeling was also conducted to evaluate the effect of dielectric properties, fiber depth, and fiber clumping on surface thermal profile. The results of simulations indicate that increase in fiber depth results in lower surface temperature, due to lower heating associated with induced surface current. Based on AMT measurement results, samples with higher fiber contents were shown to undergo greater increase in surface temperature, as observed for samples with 1 and 2 % fibers. However, this tendency was reversed with further fiber addition from 2 to 3 %, due to the potential of fiber clumping. Furthermore, the fiber clumping and lower level of fiber homogeneity for FRCM with 3 % fiber resulted in 55 % lower flexural toughness compared to the FRCM containing 2 % fiber. The results of fiber homogeneity measured from freshly cast prism were found to correlate well with those obtained from AMT technique determined on hardened samples.

— Microwave material characterization is an important nondestructive evaluation tool, as many phy... more — Microwave material characterization is an important nondestructive evaluation tool, as many physical and chemical properties can be related to a material's dielectric properties. These properties can be measured using a number of methods including the loaded waveguide technique. This method requires that a sample be placed in a waveguide sample holder and subsequently utilizes measured complex reflection (S 11) and transmission (S 21) properties to calculate the sample's dielectric properties. As such, it is important that the sample be prepared carefully, as the dielectric property calculation assumes a perfect (ideal) sample geometry. However, in practice, samples are oftentimes prepared by hand, resulting in a distorted sample geometry. This paper presents a simulation and measurement study on a number of potential sample preparation errors and the effect of these errors on calculated dielectric properties. Finally, a statistical analysis (including mean, standard deviation, coefficient of variation, and confidence interval) was applied to provide a method by which calculated dielectric properties (even when imperfect samples are used) can be checked to ensure that proper accuracy of the results has been achieved.

Health monitoring of infrastructure is very important in the transportation and infrastructure i... more Health monitoring of infrastructure is very
important in the transportation and infrastructure industries.
Many nondestructive testing (NDT) techniques have been applied
for structural health monitoring including microwave NDT,
ultrasound, thermography, etc. Due to the complex materials
(composites, concrete, etc.) commonly used, it may be difficult to
thoroughly inspect a structure using one method alone. Thus,
hybrid NDT methods have also been developed. Recently, the
integration of microwave NDT and thermography, herein
referred to as Active Microwave Thermography (AMT), has also
been considered as a potential structural health monitoring tool.
This hybrid method uses microwave energy to heat a structure of
interest, and then the thermal surface profile is measured using a
thermal camera. This paper investigates the potential of AMT to
inspect rehabilitated cement-based structures. Preliminary
simulations and measurements provided herein indicate that
AMT has the potential to detect delaminations under carbon
fiber patches bonded to concrete.

Inspection of carbon fiber reinforced polymer (CFRP) composites is very important in the aeronau... more Inspection of carbon fiber reinforced polymer
(CFRP) composites is very important in the aeronautical and
transportation industries. Many nondestructive testing (NDT)
techniques have been applied for health monitoring including
ultrasound, thermography, etc. Although thermography has been
widely used for this purpose, it often requires powerful heat
lamps which may increase the risk of (thermal) damage to the
structure under test. Thus, hybrid NDT methods have also been
developed. Recently, the integration of microwave heating and
thermography, herein referred to as Active Microwave
Thermography (AMT), has also been considered as a potential
health monitoring tool for infrastructure. This hybrid method
uses microwave energy to heat a structure of interest, and
subsequently the thermal surface profile is measured using a
thermal camera. This paper investigates the potential of AMT for
inspection of CFRP-rehabilitated airframes. Preliminary
simulations and measurements indicate that AMT has the
potential to detect disbonds under carbon fiber patches bonded
to aluminum.

In this article, an integrated broadband planar monopole antenna with extra frequency bands is pr... more In this article, an integrated broadband planar monopole
antenna with extra frequency bands is presented. The proposed antenna
consists of a simple square shaped planar. The center part of the plate
can be removed with negligible effect on reflection coefficient. To
improve the impedance matching of the planar antenna, the lower corner
of the antenna is removed. Also, the higher cut-off frequency is
enhanced by an additional strip at the top corner of the plate. By inserting
additional strips in the path of the notched part of the plate, integrated
broadband antenna with extra bands can be attained which leads
to dual- and triple-band antenna. The additional bands cover 1.71–1.88
(DCS) and 2.4–2.48 (WLAN). Simulation and measurement results of the
proposed antenna agree well and show good performance for multiband
behavior.

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, Jun 2012

IET Microwaves, Antennas & Propagation, Nov 2012

In this article, an integrated broadband planar monopole antenna with extra frequency bands is pr... more In this article, an integrated broadband planar monopole antenna with extra frequency bands is presented. The proposed antenna consists of a simple square shaped planar. The center part of the plate can be removed with negligible effect on reflection coefficient. To improve the impedance matching of the planar antenna, the lower corner of the antenna is removed. Also, the higher cut-off frequency is enhanced by an additional strip at the top corner of the plate. By inserting additional strips in the path of the notched part of the plate, integrated broadband antenna with extra bands can be attained which leads to dual- and triple-band antenna. The additional bands cover 1.71–1.88 (DCS) and 2.4–2.48 (WLAN). Simulation and measurement results of the proposed antenna agree well and show good performance for multiband behavior.

Microwave & RF, Apr 2013

This compact, circularly polarized, dual-band antenna provides sufficient bandwidth making it ide... more This compact, circularly polarized, dual-band antenna provides sufficient bandwidth making it ideal for GSM and UMTS base-station applications.

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Mar 2013

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Jul 2011

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, May 2012

The non-uniform distribution of steel fibers in fiber-reinforced cement-based mortars (FRCMs) can... more The non-uniform distribution of steel fibers in fiber-reinforced cement-based mortars (FRCMs) can lead to heterogeneous properties of hardened material with direct impact on mechanical properties. Among various nondestructive testing techniques, the active microwave thermography (AMT) has shown good potential for inspection of cement-based materials. AMT utilizes combination of microwave energy to generate controlled and localized heating and uses commercially-available infrared cameras to capture surface thermal images in real-time. Utilizing AMT, four FRCM samples made with different steel fiber volumes ranging from 0 to 3 % were investigated to evaluate the feasibility of this method for detecting and quantifying fiber distribution. Full-wave coupled electromagnetic-thermal numerical modeling was also conducted to evaluate the effect of dielectric properties, fiber depth, and fiber clumping on surface thermal profile. The results of simulations indicate that increase in fiber depth results in lower surface temperature, due to lower heating associated with induced surface current. Based on AMT measurement results, samples with higher fiber contents were shown to undergo greater increase in surface temperature, as observed for samples with 1 and 2 % fibers. However, this tendency was reversed with further fiber addition from 2 to 3 %, due to the potential of fiber clumping. Furthermore, the fiber clumping and lower level of fiber homogeneity for FRCM with 3 % fiber resulted in 55 % lower flexural toughness compared to the FRCM containing 2 % fiber. The results of fiber homogeneity measured from freshly cast prism were found to correlate well with those obtained from AMT technique determined on hardened samples.

— Microwave material characterization is an important nondestructive evaluation tool, as many phy... more — Microwave material characterization is an important nondestructive evaluation tool, as many physical and chemical properties can be related to a material's dielectric properties. These properties can be measured using a number of methods including the loaded waveguide technique. This method requires that a sample be placed in a waveguide sample holder and subsequently utilizes measured complex reflection (S 11) and transmission (S 21) properties to calculate the sample's dielectric properties. As such, it is important that the sample be prepared carefully, as the dielectric property calculation assumes a perfect (ideal) sample geometry. However, in practice, samples are oftentimes prepared by hand, resulting in a distorted sample geometry. This paper presents a simulation and measurement study on a number of potential sample preparation errors and the effect of these errors on calculated dielectric properties. Finally, a statistical analysis (including mean, standard deviation, coefficient of variation, and confidence interval) was applied to provide a method by which calculated dielectric properties (even when imperfect samples are used) can be checked to ensure that proper accuracy of the results has been achieved.

Health monitoring of infrastructure is very important in the transportation and infrastructure i... more Health monitoring of infrastructure is very
important in the transportation and infrastructure industries.
Many nondestructive testing (NDT) techniques have been applied
for structural health monitoring including microwave NDT,
ultrasound, thermography, etc. Due to the complex materials
(composites, concrete, etc.) commonly used, it may be difficult to
thoroughly inspect a structure using one method alone. Thus,
hybrid NDT methods have also been developed. Recently, the
integration of microwave NDT and thermography, herein
referred to as Active Microwave Thermography (AMT), has also
been considered as a potential structural health monitoring tool.
This hybrid method uses microwave energy to heat a structure of
interest, and then the thermal surface profile is measured using a
thermal camera. This paper investigates the potential of AMT to
inspect rehabilitated cement-based structures. Preliminary
simulations and measurements provided herein indicate that
AMT has the potential to detect delaminations under carbon
fiber patches bonded to concrete.

Inspection of carbon fiber reinforced polymer (CFRP) composites is very important in the aeronau... more Inspection of carbon fiber reinforced polymer
(CFRP) composites is very important in the aeronautical and
transportation industries. Many nondestructive testing (NDT)
techniques have been applied for health monitoring including
ultrasound, thermography, etc. Although thermography has been
widely used for this purpose, it often requires powerful heat
lamps which may increase the risk of (thermal) damage to the
structure under test. Thus, hybrid NDT methods have also been
developed. Recently, the integration of microwave heating and
thermography, herein referred to as Active Microwave
Thermography (AMT), has also been considered as a potential
health monitoring tool for infrastructure. This hybrid method
uses microwave energy to heat a structure of interest, and
subsequently the thermal surface profile is measured using a
thermal camera. This paper investigates the potential of AMT for
inspection of CFRP-rehabilitated airframes. Preliminary
simulations and measurements indicate that AMT has the
potential to detect disbonds under carbon fiber patches bonded
to aluminum.

In this article, an integrated broadband planar monopole antenna with extra frequency bands is pr... more In this article, an integrated broadband planar monopole
antenna with extra frequency bands is presented. The proposed antenna
consists of a simple square shaped planar. The center part of the plate
can be removed with negligible effect on reflection coefficient. To
improve the impedance matching of the planar antenna, the lower corner
of the antenna is removed. Also, the higher cut-off frequency is
enhanced by an additional strip at the top corner of the plate. By inserting
additional strips in the path of the notched part of the plate, integrated
broadband antenna with extra bands can be attained which leads
to dual- and triple-band antenna. The additional bands cover 1.71–1.88
(DCS) and 2.4–2.48 (WLAN). Simulation and measurement results of the
proposed antenna agree well and show good performance for multiband
behavior.

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, Jun 2012

IET Microwaves, Antennas & Propagation, Nov 2012

In this article, an integrated broadband planar monopole antenna with extra frequency bands is pr... more In this article, an integrated broadband planar monopole antenna with extra frequency bands is presented. The proposed antenna consists of a simple square shaped planar. The center part of the plate can be removed with negligible effect on reflection coefficient. To improve the impedance matching of the planar antenna, the lower corner of the antenna is removed. Also, the higher cut-off frequency is enhanced by an additional strip at the top corner of the plate. By inserting additional strips in the path of the notched part of the plate, integrated broadband antenna with extra bands can be attained which leads to dual- and triple-band antenna. The additional bands cover 1.71–1.88 (DCS) and 2.4–2.48 (WLAN). Simulation and measurement results of the proposed antenna agree well and show good performance for multiband behavior.

Microwave & RF, Apr 2013

This compact, circularly polarized, dual-band antenna provides sufficient bandwidth making it ide... more This compact, circularly polarized, dual-band antenna provides sufficient bandwidth making it ideal for GSM and UMTS base-station applications.

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Mar 2013

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Jul 2011

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, May 2012