Research Highlights

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Brief descriptions are given below to a few examples of recent research work conducted in the THz-FTIR facility.

Evaluation of Structural Integrity of Wind Turbines

The evaluation of the structural integrity of U.S. wind farm establishments has made considerable improvement by using state-of-the-art THz technology.  CNDE recently conducted a promising feasibility study, signifying the superior capability of THz in determining the structural health of the turbine blades installed in massive windmills all around the nation.

The energy generated from these wind farms has proven a viable source.  Given the global fuel shortage and recent economic downturn, the demands for wind energy are growing fast.  Consequently, assessing the structural integrity of the wind energy systems, particularly their key components of turbine blades, has also become a pressing issue in NDE.  However, the structures of the turbine blades, consisting of complicated layers of mixed materials, have posed a difficult inspection problem to conventional NDE techniques.  For instance, a wavy microstructure (“wrinkle”) embedded in the glass fiber-reinforced plastic (GFRP) laminates of the turbine blades represents a manufacturing anomaly.  With its exceptional time and spatial resolutions, THz can reveal the wrinkles and quantify their aspect ratios precisely.  This work not only pushes forward NDE research in general, but also contributes to the windpower industry in the home state of Iowa, which is a leading wind energy-producing state in the country.


(left) One of the Iowa wind farms; (right) THz imaging in action: a fiberglass laminate sample containing 7 simulated “wrinkles” is being scanned in reflection mode.



(left) C- and (right) B-scans clearly reveal the 7 “wrinkle” profiles (within the dashed box) in the fiberglass laminate.


Assessment of Chemical Contamination in Plastic Pipes of Water Distribution Systems

Plastic pipes such as polyvinyl chloride (PVC) and polyethylene (PE) are widely used in water distribution systems for the conveyance of drinking water.  The longevity and structural integrity of the plastic pipes and the elastomeric gaskets for pipe joints are impacted by contaminated soils as a result of leaks from underground storage tanks, chemical spills, and improper disposal of used chemicals.  Also of importance is the permeation of chemicals through the pipe materials or gaskets into the drinking water, which increases the health risk of consumers.  Previous attempts to address these problems using NDE methods like near infrared have not been successful.

Recently CNDE, teaming up with Professor Say-Kee Ong’s group in the Department of Civil, Construction and Environmental Engineering, demonstrated the feasibility of using THz to evaluate the physical condition and well-being of these plastic pipes.  The preliminary results were quite encouraging.  The research team was able to not only detect the presence of chemical contaminants, but also quantify the depth permeation into the pipe wall with high precision.  This novel technique will have great impact on solving similar problems such as in the petroleum industry, where oil pipelines are increasingly replaced by polymeric composites.


(left) Contaminated (left half portion) PVC pipe sample, and (right) its image under THz.


The comparison of gasoline permeation advancing in the PVC pipe vs. days of contamination between THz detections (denoted as Direct d) and destructive sectioning examined under microscopy.


Fun Stuff

This section highlights some other fun things we have done with THz – with an eye on their potential applications in biomed, agriculture, food safety, quality control, ergonomics, and design cycle.


(left) Fresh autumn leaves taken outside the THz facility (shown with a 15-cm ruler) and (right) their corresponding images under THz.  Can you spot a piece of plastic tape in the image?




(top row) THz imaging of a floss box again demonstrates THz’s time-resolved ability to “peel” through the interior of a structure: (bottom row, left to right) top skin, below top skin and middle floss core.


Fascinated with the THz technology as we are?  Please contact Thomas Chiou for further information regarding facility use, collaboration opportunities and student experience