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Flexural-Torsional Buckling Analysis of Thin- walled Composite Beams with Symmetric Layup

Sadrzadeh, Mohammad Hossein | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40581 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Haddadpour , Hassan
  7. Abstract:
  8. In the present work, the buckling behavior of a composite beam with circular, rectangular and pentagonal cross sections is investigated. The structural model is based on the first order shear deformation theory (FSDT) and incorporates other non-classical effects such as primary and secondary warpings and restrained warping. The linear buckling equations are derived from the non-linear governing equations of motion and their associated boundary conditions and solved using the Galerkin method for a composite beam with the clamped-free end condition and the special layup configuration of Circumferentially Asymmetric Stiffness (CAS) which induces elastic couplings between torsional and flexural behaviors of the structure. The set of linear equations resulting from the application of the Galerkin method are then cast into an eigen value problem which upon numeric solution, gives the critical axial load corresponding to the global buckling of the beam structure. This set of equations is presented in the form of a unified matrix relation applicable to both buckling and response analyses of the beam under static axial end loading. The buckling results obtained from the present analytical study were verified through comparison with similar works in the literature and finite element analysis. Having been verified, the present work was used to study the effect of different factors, among them different types of warpings, the height to length ratio, shear deformation and elastic couplings on the buckling behavior of the composite beam structure under study. Also the possibility of omitting the geometric couplings caused by insufficient cross sectional symmetry with the aid of elastic couplings, created as the result of using composite material, was studied during the present analysis. This required a comprehensive understanding of the position of the shear center and centroid in the thin walled composite closed section beams. To this end, an independent study was conducted and several methods were suggested to find the position of shear center and centroid in such structures.

  9. Keywords:
  10. Galerkin Method ; Waviness ; Flexural-Torsional Buckling ; Non-Classical Effects ; Circumferentially Asymmetric Stiffness (CAS)Layup Configuration ; Thin Walled Composite Beam

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