BUCKLING AND POSTBUCKLING INVESTIGATIONS OF IMPERFECT CURVED STRINGER-STIFFENED COMPOSITE SHELLS .A. EXPERIMENTAL INVESTIGATION AND EFFECTIVE WIDTH EVALUATION

A box-like stringer-stiffened thin-walled CFRP structure was subjected to load cases well beyond the limits of local buckling. The developme nt of the deflection pattern was recorded via optical means and analys ed numerically. In addition, the structure was modelled and analysed u sing the MARC FE program in the nonlinear deflection range. The geomet rical imperfections of the test structure were recorded by mechanical scanning and optical methods and introduced into the mathematical mode l. For the perfect ('ideal') and the geometrically imperfect ('real') structural model, the results of the FE analyses were compared and use d to judge the effect of geometric imperfections on the postbuckling b ehaviour of the structure. The effective axial stiffness for the vario us postbuckling states was evaluated and related to analytical estimat es of effective width values for orthotropic sheet-like panels.