Aircraft fatigue damage inspection

Currently to inspect for fatigue damage around fasteners in multi-layer structures requires either removing the fastener entirely or a perfect sealant layer between the layers for ultrasonic testing.  We propose developing a novel inspection system that uses acoustic emission to inspect the multi-layer structures.  Our approach does not require removing, modifying, or altering in any way the fastener nor the multi-layer structure.  During Phase I we will develop the initial prototypical design of our inspection system, construct a prototype, and demonstrate its ability to detect corner flaws in the multi-layer structure around fasteners.  Future efforts will be devoted to moving from the lab to the field to provide the Air Force with a practical, easy-to-use inspection solution.  TRI is currently using the LAHMP AE system to monitor fatigue cracks in C-5 skins.  The lessons learned in this internally funded C-5 project will form the basis for the proposed Phase I work. BENEFIT: Studies have shown that reducing the number of fastener removals required for inspection can save the Air Force millions, as much as $65 million dollars for the B-1B alone.  Since our system drops the number of fastener removals to zero, we anticipate that even more significant savings can be realized by the Air Force.  In addition, due to the ubiquitous nature of multi-layer structures in aerospace, we anticipate similar savings can be realized by the Navy, Marines, and commercial airlines.