FRACTURE-MECHANICS OF PLATES AND SHELLS APPLIED TO FAIL-SAFE ANALYSISOF FUSELAGE .2. COMPUTATIONAL RESULTS

In this paper, the problem of the fracture of a fuselage stiffened by longitudinal longerons and circumferential frames is analyzed by means of the finite element method. Our research is motivated by the fail-s afety design concept of fuselage for civil aircraft. In this study, th e total energy release rate are evaluated for five types of basic load ing, namely, axial extension, pure bending, twisting, transverse shear ing, and radial expansion due to internal pressure. The crack is locat ed either at the mid-point or near the end of the fuselage. It extends in two bays with the stiffener al its center. The stiffener which bis ects the crack is assumed to be broken at the location of the crack. C omputational results indicate that the total energy release rate G(t) increases with the increasing crack length. However, when the crack ti p approaches the stiffener, the value of G(t) decreases as a result of the reinforcement from the stiffener. For a crack near the end of the fuselage, as a result of boundary effect, the value of G(t) is larger in comparison with the case of the crack at the mid-point of the fuse lage. We also find that the effect of geometrical nonlinearity can red uce the value of G(t) for the fuselage under axial tension or pure ben ding. For the fractured fuselage under pure bending, shell buckling ca n occur at the concave side of the fuselage prior to crack growth. The maximum tensile stress in the stiffener in front of the crack tip is also investigated. (C) 1997 Elsevier Science B.V.