Applications of Advanced Fracture Mechanics to Fuselage

Summary

Multi-site damage (MSD) in the form of cracking at rivet holes in lap splice joints has been identified as a serious threat to the integrity of commercial aircraft nearing their design life targets. Consequently, to assure the safety of aircraft that have accumulated large numbers of flights, flight hours and years in service requires inspection procedures that are based on the possibility that MSD may be present For inspections of aircraft components to be properly focused on the defect sizes that are critical for structural integrity, fracture mechanics analyses are needed. The current methods are essentially those of linear elastic fracture mechanics (LEFM) which are strictly valid only for cracks that extend in a quasi-static manner under small-scale crack tip plasticity conditions. While LEFM is very likely to be appropriate for subcritical crack growth, quantifying the conditions for fracture instability and subsequent propagation may require advanced fracture mechanics techniques. The specific focus in this paper was to identify the conditions in which inelastic-dynamic effects occur in (1) the linking up of local damage in a lap splice joint to form a major crack, and (2) large-scale fuselage failure by a rapidly occurring fluid/structure interaction process.