Critical Surface Stresses of Buckled Composite Plates
Sprache des Vortragstitels:
GAMM 2011 - 82nd Annual Meeting of the International Association of Applied Mathematics and Mechanics
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Laminated composite structures are very sensitive to compressive loading. Particularly the allowable compressive stress after impact damage can be significantly lower than the nominal strength value of the undamaged structure. Thus the strength design of composites is often driven by the maximum compressive stresses in the structure.
Considering a plate under uni-axial compression it is well-known that after buckling the stresses concentrate at the unloaded edges. The out-of-plane displacement at the buckle causes an in-plane relaxation, which decreases the mid-plane stresses towards the plate center. This stress distortion is described by the so-called effective width. The knowledge of the effective width allows the calculation of the stress at the unloaded edges, which is then usually considered as the critical stress in the compressed plate. However, the out-of-plane displacement at the buckle causes also bending stresses, which produce additional compression. Here the
fundamental question arises, under which circumstances the total stress at the surface of the buckle is the critical one, i.e. higher than the stress at the unloaded edges. In this contribution
analytical formulas for engineering application are presented. Derived from higher-order theories these formulas approximate the magnitude of the surface stresses in a compressed buckled plate and assess at which plate dimensions and load levels these surface stresses become critical.