Structural Health Monitoring of a Bonded Composite Patch Repair on a Fatigue-Cracked F-111C Wing
Abstract
A large fatigue crack in the wing skin of an Australian Defence Force F-111C aircraft was repaired with an adhesively bonded boron/epoxy fibre composite patch. The patch prevented further growth of the crack for 670 flying hours. To aid in the continued safe operation of ADF F-111 aircraft, a decision was later made to assess the residual life of the F-111 wings in part by undertaking a fatigue test at DSTO on a retired wing. An additional aim of the test was to substantiate further the bonded repair, in view of its potential application to other F-111 aircraft either as a repair for cracked wings or as reinforcement to inhibit fatigue crack formation in uncracked wings. The test importantly would also evaluate the effectiveness of non-destructive inspection (NDI) and other non-destructive procedures to detect crack growth under the patch or disbonding of the patch system. The repaired wing was therefore selected and used for this study. In this test the patch was successful in preventing growth of the crack for around a further 9000 simulated flying hours. As a consequence of NDI indications of local patch disbonding and concern that it could lead to rapid growth of the repaired crack and thus premature failure of the wing a structural health monitoring (SHM) technique was implemented to monitor the patch. This report, after providing background to the repair and its performance, describes a) the comparison of NDI results for crack detection with the fractographic studies on the crack after the tear down and b) the comparison of the NDI and SHM results for disbonding with bond-strength measurements on the patch system undertaken at the completion of the fatigue test.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 2008
- Accession Number
- ADA485406
Entities
People
- Alan Baker
Organizations
- Defence Science and Technology Group