The development of nondestructive testing (NDT) techniques for detecting and characterizing disbonds in honeycomb sandwich structures is often hampered by the lack of test articles that contain known discontinuities. This paper describes a method for producing controlled, realistic and often nearly invisible disbonds on actual honeycomb sandwich components. The method uses localized heating on the facesheet to create disbonds from the honeycomb core in a variety of metallic and composite sandwich structures removed from an aircraft. In addition, heat cycling to a temperature below that which causes disbonding is used as a way to degrade the bond strength to different degrees. Heat-induced disbonding and degradation on a slat wedge are detected and imaged by a number of NDT techniques in a round-robin test.
Barnard, D.J. and D.K. Hsu, “A Scan for All Seasons: Development of a
Generic Manual Scan System,” 9th Joint FAA/DoD/NASA Conference on
Aging Aircraft, CD Proceedings, 2006.
Barnard, D.J., D.K. Hsu and J.J. Peters, “Development, Field and Beta Tests
of a Generic Manual Scanner,” Review of Progress in Quantitative Nondestructive
Evaluation, Vol. 26B, D.O. Thompson and D.E. Chimenti, eds.,
Melville, New York, AIP, 2007, pp. 1707–1714.
Hsu, D.K., J.J. Peters, D. Fei, D.J. Barnard and V. Dayal, “Imaging of Flaws
in Composite Honeycomb Aircraft Structures Using Instrumented Tap
Test,” Proceedings of SPIE on Nondestructive Evaluation of Aging Materials
and Composites III, Vol. 3585, 1999, pp. 236–245.
Hsu, D.K., D.J. Barnard, J.J. Peters and V. Dayal, “Physical Basis of Tap
Test as a Quantitative Imaging Tool for Composite Structures on Aircraft,”
Review of Progress in Quantitative Nondestructive Evaluation, Vol. 19B, D.O.
Thompson and D.E. Chimenti, eds., Melville, New York, AIP, 2000, pp.
1857–1864.
Hsu, D.K. and D.J. Barnard, “Inspecting Composites with Airborne Ultrasound:
Through Thick and Thin,” Review of Progress in Quantitative Nondestructive
Evaluation, Vol. 25B, D.O. Thompson and D.E. Chimenti, eds.,
Melville, New York, AIP, 2006, pp. 991–998.
Newman, J.W., “Holographic and Shearographic Applications in Aerospace
Manufacturing,” Materials Evaluation, Vol. 63, 2005, pp. 746–750.
Peters, J.J., D.J. Barnard, N.A. Hudelson, T.A. Simpson and D.K. Hsu, “A
Prototype Tap Test Imaging System: Initial Field Test Results,” Review of
Progress in Quantitative Nondestructive Evaluation, Vol. 19B, D.O.
Thompson and D.E. Chimenti, eds., Melville, New York, AIP, 2000, pp.
2053–2060.
Radtke, T.C., A. Charon and R. Vodicka, “Hot/Wet Environmental Degradation
of Honeycomb Sandwich Structure Representative of F/A-18:
Flatwise Tension Strength,” Australian DSTO Technical Report, No. 0908,
Canberra, Australia, Defence Science and Technology Organisation, 1999.
Roach, D. and L. Dorrell, “Development of Composite Honeycomb and
Solid Laminate Reference Standards to Aid Aircraft Inspections,” NDT.net,
Vol. 4, No. 3, 1999.
Shepard, S.M., J.R. Lhota, B.A. Rubadeux, D. Wang and T. Ahmed,
“Reconstruction and Enhancement of Active Thermographic Image
Sequences,” Optical Engineering, Vol. 42, 2003, pp. 1337–1342.
Sun, J.G., Method for Thermal Tomography of Thermal Effusivity from Pulsed
Thermal Imaging, US Patent No. 7,365,330, issued April 29, 2008.