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Water ingress inside honeycomb sandwich panels during service has been linked to in-flight failure in some aircraft. There is an ongoing effort to develop nondestructive testing methods to detect the presence of water within the panels. Magnetic resonance (MR) represents an attractive approach in that it is sensitive to moisture. Using a unilateral MR sensor, testing can be applied directly to the surface of the panel. The viability of MR is demonstrated through laboratory imaging of both water within sandwich panels, as well as the adhesive itself. The detection of water using a one-sided handheld MR sensor is presented. It is shown that simple detection, as well as spatial localization of water within sandwich panels is possible.

Gamma-ray Compton scattering is used for the detection of debonding in adhesively bonded composite-aluminum joints. A collimated narrow beam of monochromatic photons, generated by a 137 CS source, is directed towards the joint and scattered photons are recorded, using a detector located on the same side as the source. The energy of the scattered radiation is measured and related to the angle of scattering. The occurrence of debonding is indicated by a change in the count rate at an energy corresponding to its location. The performance of the technique is successfully demonstrated experimentally for joints of different adhesive-bonding thicknesses and for artificially induced debonds.