Global-Local Flexural-Torsional Buckling of Composite Laminated Beams

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Classical stability problems like global buckling (i.e. flexural buckling, flexural-torsional buckling, lateral buckling) as well as local buckling problems such as web or flange buckling of thin-walled isotropic beams have been understood and can be treated adequately using analytical or numerical methods. A significant number of open questions, however, exist when dealing with the stability behavior of shear deformable and anisotropic beams made of composite laminated materials. The present research proposal is thus devoted to the investigation of the flexural-torsional buckling problem of such composite laminated beams under consideration of simultaneous local buckling modes where the focus is on the development of highly efficient and accurate closed-form and semi-analytical methods. The simultaneous occurrence of local and global buckling modes is often termed as interactive buckling or global-local buckling and has been treated only scarcely in the open literature. The analysis methods that shall be developed in this research project are intended to incorporate all coupling effects as they are typical in composite laminates, as well as the influence of transverse shear deformations that have a significant influence on the buckling response of laminated structures which necessitates the use of higher order shear deformation theories. The research project will focus on the development of closed-form analytical and semi-analytical methods for the assessment of the flexural-torsional buckling of composite laminated beams under uniaxial compression considering local buckling modes wherein a hierarchical modelling concept will be employed by using several different laminate theories (Classical laminated plate theory as well as First-Order and Third-Order Shear Deformation Theory) for the local buckling modes. The analysis methods are based on energy formulations in conjunction with the Ritz method using adequate representations for all buckling degrees of freedom using series expansions. A comparison with finite element computations and reference results will serve as method verification. Systematic optimization routines using the methods of mathematical programming will be employed in order to highlight the optimization potential for composite laminated beams when interactive buckling is considered.