Nondestructive evaluation of crack propagation under a composite patch repair using the eddy current method

Zaira P. Marioli-Riga; George J. Tsamasphyros; Georgios N. Kanderakis

doi:10.1117/12.385021

5 May 2000 Nondestructive evaluation of crack propagation under a composite patch repair using the eddy current method

Zaira P. Marioli-Riga, George J. Tsamasphyros, Georgios N. Kanderakis

Proceedings Volume 3994, Nondestructive Evaluation of Aging Aircraft, Airports, and Aerospace Hardware IV; (2000) https://doi.org/10.1117/12.385021
Event: SPIE's 5th Annual International Symposium on Nondestructive Evaluation and Health Monitoring of Aging Infrastructure, 2000, Newport Beach, CA, United States

Abstract

The eddy current method is used to trace crack propagation under a composite patch repair of a cracked metallic structure, after mechanical testing in fatigue. The capability and the reliability of the eddy-current method to detect cracks under a composite obstacle of significant thickness are checked for several patch thicknesses. Notched specimens 6 mm thick were fabricated using 2024-T3 Aluminum. Boron Epoxy patches bonded with film adhesive were applied to the one side of the metallic specimens. Initial notches were 10 mm long, while the thickness of the reinforcement was varying from 2 layers (0.25 mm) to 7 layers (0.875 mm) in order to represent actual structural composite patch repairs. Crack propagation from the tip of the notches was achieved by fatigue loads. The estimation of required loads to cause fatigue crack propagation was done by means of three-dimensional finite elements analysis. The eddy current method was then applied to trace the crack tip under the patch after their mechanical testing. Accuracy of the eddy-current method was verified by measuring the crack lengths on both sides of the specimen and comparing the results. The eddy-current method was found to be fully capable of tracing the crack propagation under the composite patch, requiring only proper calibration for the generator. Small differences in the crack lengths between the patched and the unpatched side of the specimen were explained by their non-symmetric configuration, which induced different stress intensity factors at the patched and the unpatched sides, as finite elements analysis has clearly shown.

Citation Download Citation

Zaira P. Marioli-Riga, George J. Tsamasphyros, and Georgios N. Kanderakis "Nondestructive evaluation of crack propagation under a composite patch repair using the eddy current method", Proc. SPIE 3994, Nondestructive Evaluation of Aging Aircraft, Airports, and Aerospace Hardware IV, (5 May 2000); https://doi.org/10.1117/12.385021

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