23 February 2018 Non-destructive evaluation of GFRP-wood sandwich structure composite using terahertz imaging
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Engineering of novel structures with high strength to weight ratio for applications in aerospace, renewable energy and naval industries has resulted in an increased popularity of sandwich structured composites. A sandwich-structured composite is fabricated by bonding a thick lightweight core between two stiff, thin skins such as Glass Fiber Reinforced Plastic (GFRP). Balsawood is a type of homogeneous core which is widely used for renewable energy structures, such as wind turbine blades. In this paper, a GFRP-balsawood sandwich structure is evaluated non-destructively for internal defects such as holes, using a CW Terahertz system in transmission mode. Internal defects will give rise to differential THz transmission and hence can be identified using THz imaging. The imaging studies are carried out with a central frequency of 0.35 THz and the sample is raster scanned using 2-D translational stages controlled by high precision stepper motors in x-y directions to obtain the THz image. The image acquired using CW THz system clearly identifies the defects in the GFRP-balsawood composite structure with good contrast demonstrating the potential of THz imaging for non-destructive testing of sandwich composite structures.
Conference Presentation
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Harikrishnan Kaimal, Harikrishnan Kaimal, Nirmala Devi, Nirmala Devi, Shaumik Ray, Shaumik Ray, Prabhu Rajagopal, Prabhu Rajagopal, Krishnan Balasubramanian, Krishnan Balasubramanian, Bala Pesala, Bala Pesala, } "Non-destructive evaluation of GFRP-wood sandwich structure composite using terahertz imaging", Proc. SPIE 10531, Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications XI, 105310D (23 February 2018); doi: 10.1117/12.2289718; https://doi.org/10.1117/12.2289718

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