Closed disbond detection in marine glass-epoxy/balsa composites

A method is devised and demonstrated for the detection of disbonds in E-glass-epoxy/end-grain balsa core composites. Guided acoustic waves are exploited in an approach that leads to positive identification of disbonds in these complex marine composites. The method uses the fact that a propagating Lamb wave in the 3-mm glass-epoxy facesheet composite will exist only when a disbond (even a disbond in partial contact) is present at the location of the incident acoustic beam. The resulting leaky wave field in the fluid is then detected and monitored over the scanned area, producing a C-scan of the interface with clear discrimination between bonded areas and disbonds. Numerical evaluations of the received transducer voltage corresponding to different interface conditions are compared with the experimental measurements. A theoretical calculation based on prior work predicts accurately the results of several experiments on a variety of samples with different disbond conditions.