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Ali Foudazi1, Iman Mehdipour2,
Kristen M. Donnell1, and Kamal Khayat2
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14th Int. Symp. on Nondestructive Characterization of Materials (NDCM 2015) - www.ndt.net/app.NDCM2015
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� '- & mm-Wave NDT
� Thermography
� Active Microwave Thermography (AMT)
� Steel-Fiber Reinforced Cement-based (SFRC) materials
� Objective – Evaluation of Fiber Orientation
� Mechanical Strength of SFRC materials
� AMT measurement of SFRC materials
� Concluding Remarks
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� Thickness of dielectric sheets, coatings, etc.
� Thickness variation/quality control.
� Disbond, delamination, voids & porosity.
� Defect/inhomogeneity in dielectrics.
� Corrosion detection under paint and other coatings.
� Composition of dielectric materials.
� Excess moisture in composites.
� Cure state evaluation and monitoring.
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� Thick sandwich composite inspection.
� Defect size, properties & image.
� Surface cracks, anomalies & perturbations in metals
and graphite composites.
� Relating microwave properties to physical &
mechanical attributes of materials.
� Conductor & dielectric sheet surface profiling.
� …
� '- & mm-Wave NDT may result in lengthy inspection
times for inspection of SFRC materials.
������������� Advantages:
� Fast and real time inspection
� Well-established
� Easy to use
� Disadvantages:� Risk of heat damage
� Non-uniform heating
� Localized heating not possible
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Object Under Test
Microwave Energy(heat source)
Thermal Camera
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� Interaction between '-wave and materials
causes heating due to Dielectric Propertiesof materials (lossy materials).
� Describes the ability of a material to store (real part) and absorb (imaginary part) microwave energy.
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� Heating due to Induced Surface Current distributed on conductive materials irradiated by '-wave energy.
� Example of conductive materials:
� CFRP
� Steel bar (Rebar)
� Steel-Fibers
"������������� Availability of fast and sensitive commercial IR cameras -
thermography is readily deployable.� Application of microwave energy can be tailored to the
inspection need.� Design the incident signal to heat specific dielectric.
� Localized heating.
� May also reduce risk of heat damage to structure.
� Other electromagnetic factors – frequency, antenna design, polarization, etc.
� Thermography is well established – can capitalize on the legacy of thermography for new applications.� Advanced signal processing techniques already well established
(including for other hybrid thermography methods).
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Pieper, D., K.M. Donnell, M.T. Ghasr, and E.C. Kinzel. "Integration of Microwave and Thermographic NDT Methods for Corrosion Detection." 40TH Annual Review of
Progress in Qualitative Nondestructive Evaluation: Incorporating the 10th International Conference on Barkhausen Noise and Micromagnetic Testing, vol. 1581, no. 1, pp.
1560-1567. AIP Publishing, 2014.
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A. Foudazi., K.M. Donnell, and M.T. Ghasr. "Application of Active Microwave Thermography to Delamination Detection." 2014 Proceedings IEEE International
Instrumentation and Measurement Technology Conference (I2MTC), pp. 1567-1571, 2014.
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A. Foudazi, M.T. Ghasr, and K.M. Donnell, "Application of Active Microwave Thermography to inspection of carbon fiber reinforced composites," 2014 Proceedings IEEE AutotestCon, pp. 318-322, 2014.
Uniform Distribution Non-Uniform Distribution
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� Fiber distribution and orientation significantly
affects the mechanical performance of SFRC.
Boulekbache et al.
(2010)
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� Addition of Steel-fibers:
� Enhances post-cracking response
� Improves energy absorption capacity
� Increases crack resistance
Maccaferri, Inc.
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� Uniform fiber distribution is desired.
� In practice, non-uniform fiber distribution occurs:
� Introducing voids and entrapment of air
� Causing little or no reinforcement in some regions
� Reduced performanceIncrease Fibers
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� Destructive
� X-ray tomography
� Electrical resistivity
Ferrara et al. (2012)
Bordelon and Roesler (2014)
Barnett et al. (2010)
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� Four mortar samples with fiber dosages from
0% to 3%
� Sample dimensions: 200 × 200 × 200 mm3
� Water-to-cement ratio (w/c) = 0.45
� Sand-to-cement ratio (s/c) = 2.5
0%
1%
2%
3%
Steel Fibers shape
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� Higher dosage of steel-fibers is not always
better.
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SFRC
sample
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Mean of
Temperature riseStandard Deviation of
Temperature riseCooling Rate
2.4
GH
z3.0
GH
z
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t = 10 sec t = 20 sect = 30 sec
(End of heating)
t = 60 sec
(30 sec cooling)
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t = 10 sec t = 20 sect = 30 sec
(End of heating)
t = 60 sec
(30 sec cooling)
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Mean of
Temperature riseStandard Deviation of
Temperature rise
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� AMT is in the exploratory stage of development,
with future areas of application yet to come.
� AMT shows the potential for evaluation of steel-
fiber distribution in SFRC materials.
� AMT can be used for further study of SFRC
materials including depth and size extraction of
fibers.
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