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Portable and Noncontact Imaging System for Characterizing Composite Delamination
Professors Ken Loh and Hyonny Kim
San Diego, Calif., Oct. 22, 2020 -- Carbon fiber-reinforced polymer (CFRP) composites are widely used in various Naval aircraft structures, as well as in many civilian aerospace, automotive, and industrial structural components. However, composites can sustain complex damage modes, where even low-velocity impact can result in subsurface delamination. The aim of this research is to target the time-consuming elements of current Navy ultrasonic inspection methods and to demonstrate improved damage characterization in reduced time, while also lessening the burden on technicians to prepare, inspect, and report component damage. For this project funded by the Office of Naval Research, and in collaboration with NAVAIR ISSC North Island, the goal is to develop a noncontact, portable, nondestructive inspection system for imaging and characterizing delamination in CFRP composites. A prototype planar electrical capacitance tomography electrode array and imaging algorithm were developed. The system was used to image damaged CFRP specimens, which were subjected to hammer impact tests to induce subsurface delamination. The volumetric permittivity image, as obtained by the noncontact imaging system, revealed significant dielectric property changes near the point of impact. The results were compared with a corresponding ultrasonic C-scan image of the same specimen and confirmed the presence of subsurface damage at the center. Overall, the technology is expected to directly visualize the physical properties of the panel, as well as damage features embedded in the part.