Evaluation of scaling approach for stiffened composite flat panels loaded in compression

Results of an experimental study or the effects of geometric scaling on a g raphite-epoxy flat stiffened-skin panel concept loaded in compression are p resented. The scaled models were fabricated using an approach to laminate t hickness scaling, referred to as the "ply-thickness method." The structural response and failure characteristics of full-, half-, and quarter-scale sp ecimens fabricated with this scaling concept are discussed and compared. Th e scaled-up failure loads of the half- and quarter-scale models agree well with the failure load of the full-scale prototypes tested. The strength sca le effects observed in the results were substantially smaller than those in earlier studies that employed other laminate scaling techniques. The exper imental results indicate that failure initiated by crippling and delaminati on in the cap of the longitudinal stiffeners and skin-stiffener separation at the bond lines was followed by failure of the specimen skin. Nonlinear f inite element analysis results correlate well with experimental results up to failure.