K.-F. Nilsson, W. Hutchinson

The work concerns the development of a fracture mechanics model to analyse the capability of tear straps to arrest a propagating macrocrack in a fuselage lap-joint when multi site damage (MSD) is present. Particular emphasis is placed on the role of plastic deformation. The method accounts rigorously for the interaction between the macrocrack and the smaller MSD-cracks in a flat reinforced sheet. A special modification of the Dugdale model is used to account for the plastic deformation ahead of the macrocrack. Plastic deformation of the tear straps is included in the model as well. It is common to present the crack arrest capability by residual stress curves, i.e. the maximum stress the damaged lap-joint can sustain. In this spirit it will be shown that MSD restricts the range for which linear elastic fracture mechanics (LEFM) is applicable drastically. According to the proposed model, MSD lowers the residual stress level significantly. The capability of the tear strap to arrest an advancing major crack is, however, only slightly reduced. These features have been observed in full-scale tests of MSD-damaged aircraft panels, recently carried out at Foster Miller Inc. Several representative examples will be presented in order to bring an understanding of how the macrocrack, MSD-cracks and the tear straps interact. The computation times for the presented method are very short; it can therefore be used in practical situations, and in particular it may serve as a tool in developing a damage tolerance methodology for aging aircraft.

5th International Conference on Structural Airworthiness of New and Aging Aircraft, Hamburg, 1993

Conference Poster

englisch

21,0 x 29,7 cm, 1 Seiten

DGLR-Bericht, 1993, 1993-02, 5th International Conference on Structural Airworthiness of New and Aging Aircraft - Proceedings; S.253-253; 1993; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

structural fatigue

Bestellbar

1993