BUCKLING AND POSTBUCKLING INVESTIGATIONS OF IMPERFECT CURVED STRINGER-STIFFENED COMPOSITE SHELLS .B. COMPUTATIONAL INVESTIGATIONS

Computational investigations of the buckling and postbuckling behaviou r of a stringer-stiffened composite wing torsion box employing the fin ite element method are presented. Perfect and imperfect configurations - considering geometrical imperfections as well as initial stresses - are discussed. Two different loadcases are investigated: pure axial l oading and axial loading with a superimposed constant torsion moment. The buckling behaviour is determined by tracing the load-deflection cu rves using Riks' path-following method. Additional investigations, suc h as accompanying eigenvalue analyses and first-ply failure calculatio ns, are performed for the first loadcase. Special attention is put on the modelling of the stiffened regions, where eccentrically placed lay ers have to be taken into account doe to the bonding of the stiffeners to the inner surface of the box. The results show interesting phenome na, such as additional buckling points in the postbuckling region, whi ch, however, can hardly be detected by simply considering the load-axi al displacement path.