AN ANALYTICAL AND EXPERIMENTAL INVESTIGATION OF THE RESPONSE OF THE CURVED, COMPOSITE FRAME SKIN SPECIMENS

Six-foot diameter, semicircular graphite/epoxy specimens representativ e of generic aircraft frames were loaded quasistatically to determine their load response and failure mechanisms for large deflections that occur in airplane crashes, These frame/skin specimens consisted of a c ylindrical skin section co-cured with a semicircular I-frame. The skin provided the necessary lateral stiffness to keep deformations in the plane of the frame in order to realistically represent deformations as they occur in actual fuselage structures, Various frame laminate stac king sequences and geometries were evaluated by statically loading the specimen until multiple failures occurred, Two analytical methods wer e compared for modeling the frame/skin specimens: a two-dimensional sh ed finite element analysis and a one-dimensional, closed-form, curved beam solution derived using an energy method, Flange effectivities wer e included in the beam analysis to account for the curling phenomenon that occurs in thin flanges of curved beams. Good correlation was obta ined between experimental results and the analytical predictions of th e linear response of the frames prior to the initial failure, The spec imens were found to be useful for evaluating composite frame designs,