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From:
Victor M. Casado (1), Svend Hinsch (1), Jesús Gómez García (1), and Saullo G. P. Castro (2)
(1) Airbus Defence & Space, Bremen, Germany
(2) PFH Göttingen, Composite Engineering Campus, Stade, Germany
(2) EMBRAER, Brazilian Aerospace Company, Brazil
“Effect Of Initial Geometrical Imperfections On The Buckling Load Of Cylindrical Sandwich Shells Under Axial Compression”, DESICOS (www.DESICOS.eu), 2014 or 2015
ABSTRACT: The impact of geometrical imperfections on the general instability of laminated cylindrical sandwich shells was assessed by means of a numerical investigation. Five forms of ‘ideal’ initial geometrical imperfection patterns were studied: eigen-mode shaped, axisymmetric dimple, geometric dimple, single perturbation load and single stress-free dimple. Implementation of such imperfections, despite their simplicity, can provide a method for predicting lower-bound buckling loads during the preliminary design phase, when the structural defects of the real hardware are unknown. Numerical prediction of the non- linear instability of the cylinders under axial compression was performed using the finite element method. A typical launcher Inter Stage Skirt (ISS) structure is used as the basis for the chosen geometry and materials. In order to make design and qualification tests more affordable, it is common to use representative sub-scaled hardware. This paper verifies the validity of the chosen sub-scaling method of an ISS cylindrical shell. Buckling mechanisms are described and the different lower-bound methods are discussed.
Notice how the buckling loads (kN) are clustered. Remember the classical buckling load of a monocoque cylindrical shell is independent of the buckling mode shape (number of waves in the axial and circumferential directions).
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