Patent ID: 8386118

Claim:
A method for detecting an anomaly in a hidden portion of a first layer of a multi-layer structure, the method comprising: providing a monitoring element on at least one exposed end of a fastener that extends through the multi-layer structure; providing another monitoring element on an exposed portion of the first layer, wherein the multi-layer structure comprises a pair of opposed surface layers through which opposite ends of the fastener extend and are exposed and one or more intermediate layers including the first layer positioned between the opposed surface layers, and wherein providing another monitoring element on an exposed portion of the first layer comprises providing another monitoring element on a surface of the first layer that extends beyond at least one of the surface layers; introducing an inspection signal into the multi-layer structure including the hidden portion of the first layer with at least one of the monitoring elements; sensing the inspection signal with at least another one of the monitoring elements following the propagation of the inspection signal through at least a portion of the multi-layer structure including the hidden portion of the first layer; and detecting the anomaly in the hidden portion of the first layer based upon the inspection signal that has been sensed.