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Computational Science, Engineering & Technology Series
ISSN 1759-3158 CSETS: 15
INNOVATION IN ENGINEERING COMPUTATIONAL TECHNOLOGY Edited by: B.H.V. Topping, G. Montero, R. Montenegro
Chapter 20
Robust Design of Composite Shells: Simulation and Validation C. Hühne*, R. Rolfes* and J. Teßmer+
*Institute of Structural Analysis, University of Hannover, Germany Full Bibliographic Reference for this chapter
C. Hühne, R. Rolfes, J. Teßmer, "Robust Design of Composite Shells: Simulation and Validation", in B.H.V. Topping, G. Montero, R. Montenegro, (Editors), "Innovation in Engineering Computational Technology", Saxe-Coburg Publications, Stirlingshire, UK, Chapter 20, pp 425-444, 2006. doi:10.4203/csets.15.20
Keywords: composite shells, stability, buckling, robust design.
Summary
Thin-walled shell structures like circular cylindrical shells are prone to buckling.
Imperfections which are defined as deviations from perfect shape and perfect
loading distributions can reduce the buckling load drastically compared to that of the
perfect shell. Design criteria monographs like NASA-SP 8007 recommend that the
buckling load of the perfect shell shall be reduced by using a knockdown factor. The
existing knockdown factors are very conservative and do not account for the
structural behaviour of composite materials. To determine an improved knockdown
factor several authors consider the realistic shape of the shell in a numerical
simulation using probabilistic methods. For this probabilistic approach a large
number of test data is needed which is often not available. Motivated by this lack of
data a new deterministic approach is presented for determining the lower bound of
the buckling load of thin-walled cylindrical composite shells. It is derived from
phenomenological test data.
Previous investigations have shown that a single buckle is a realistic, worst case and
stimulating geometric imperfection of thin-walled cylindrical shells [1,2,3]. The single
pre-buckle is induced by a perturbation rig 1. The influence of a radial
perturbation load on the structural behaviour is investigated by applying loads of
different magnitudes and at different positions along the circumference. The results
of one perturbation position are shown in Figure 2. Each dot marks one test and
shows the buckling load Based on the test results the numerical analysis is validated. The results of the tests and the numerical analysis are compared to the values of the NASA-SP 8007. The new approach leads to a much less conservative, but also safe, design. The possibilities for practical use are shown using a design example. References
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