22nd Congress of International Council of the Aeronautical Sciences, Harrogate, UK, 28 August - 1st September, 2000
Paper ICAS 2000-4.2.3

LOCAL POSTBUCKLING ANALYSIS OF CURVED AEROSPACE STRUCTURES

M. Fischer, D. Kennedy
Cardiff University, UK

Keywords: post buckling analysis, curved aerospace structures, minimum mass design

Minimum mass design of aerospace structures is greatly enhanced by allowing for their postbuckling reserve of strength, which is mainly due to stress re-distribution within the structure following buckling in a local mode. The paper first outlines a geometrically nonlinear analysis for longitudinally compressed panels, in which the ratio of postbuckling to prebuckling axial stiffness is established by an iterative procedure, critical buckling loads and mode shapes being found by an ‘exact strip’ algorithm. The analysis is illustrated by its application to a simply supported, curved, stiffened panel. The paper next describes an incremental approach to the local postbuckling analysis of longitudinally stiffened cylindrical shells loaded by longitudinal compression and/or a bending moment. The shell is modelled as a collection of skin/stiffener portions, for each of which the critical buckling load and stiffness ratio are determined. Next the axial loads in each portion due to the applied loads are calculated under linear elastic assumptions, so that it is possible to determine which portion will buckle first. Thereafter the buckled portion is modelled with a reduced stiffness, so that the location of the shell’s neutral axis changes and is found by an iterative improvement to a method originally developed by Bruhn.

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