An Exploratory Study of the Application of Carbon Nanotubes to Skin Friction Measurements
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Arrays of carbon nanotubes were grown on bare 2 x 2 mm square silicon chips. The nanotubes were grown to heights of 75 microns with a thin layer of amorphous carbon on top. The silicon chips were then flipped, and the amorphous layer of carbon was bonded to bare 1 x 1 cm silicon substrates, making the bottom of 2 x 2 mm silicon chip the sensor head. The sensors were calibrated at Luna Innovations using a point-load technique. Four of the six sensors could not be successfully calibrated because they were fatally damaged during the last step of the calibration process. Wind tunnel tests were conducted on the one sensor that survived the calibration.
An arrangement was designed and built from aluminum to test the performance of the sensor in the Virginia Tech Supersonic Wind Tunnel. Seven test runs were conducted in this cold-flow facility at a nominal Mach number of 2.4 and stagnation pressures ranging from 50 - 90 psia. Two test runs gave skin friction values 3 - 20% lower than those values predicted by indirect measurement techniques before the sensor was damaged. While these first results are encouraging, further studies are clearly needed. Due to distinct anomalies in the displacement data during test run 3, it was concluded that the sensor was damaged during this run. Possible explanations of the failure of this sensor are offered along with suggestions for future work.
- Masters Theses