A Novel Methodology for Spatial Damage Detection and Imaging Using a Distributed Carbon Nanotube-Based Composite Sensor Combined with Electrical Impedance Tomography
This paper describes a novel non-destructive evaluation methodology for imaging of damage in composite materials using the electrical impedance tomography (EIT) technique applied to a distributed carbon nanotube-based sensor. The sensor consists of a nonwoven aramid fabric, which was first coated with nanotubes using a solution casting approach and then infused with epoxy resin through the vacuum assisted resin transfer molding technique. Finally, this composite sensor is cured to become a mechanically-robust, electromechanically-sensitive, and highly customizable distributed two-dimensional sensor which can be adhered to virtually any substrate. By assuming that damage on the sensor directly affects its conductivity, a difference imaging-based EIT algorithm was implemented and tailored to offer two-dimensional maps of conductivity changes, from which damage location and size can be estimated. The reconstruction is based on a newly defined adjacent current–voltage measurement scheme associated with 32 electrodes located along the boundary of the sensor. In this paper, we evaluate our methodology first by introducing well-defined damage where sections are either removed or narrow cuts are made on a series of sensor specimens. Finally, a more realistic damage scenario was investigated to show the capability of our methodology to detect impact damage on a composite laminate. The resulting EIT maps are compared to visual inspection and thermograms taken with an infrared camera.
KeywordsDistributed sensing Carbon nanotube Composite materials Nonwoven fabric Electrical impedance tomography Non-destructive evaluation Damage detection Difference imaging
The support of this collaborative research effort by the National Science Foundation, CMMI Division, Award # 1234830 (Dr. Kishor Mehta, Program Director) is greatly appreciated. The authors would like to thank Technical Fibre Products (TFP) for donating the nonwoven fabrics used in this research. We also would like to acknowledge Dr. Dirk Heider from Center for Composite Materials at University of Delaware for his supply of the infrared camera used in this research.
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