Effect of Boundary Conditions on Buckling Load for Laminated Composite Decks Plates

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Effect of Boundary Conditions on Buckling Load for Laminated Composite Decks Plates
Osama Mohammed Elmardi Suleiman Mahmoud Yassin Osman Tagelsir Hassan
[email protected] [email protected] [email protected]
Department of M. Eng.Nile Department of M. Eng. Department of M. Eng.
Valley University, Atbara, Kassala University, Kassala, Omdurman Islamic University,
Sudan Sudan Omdurman, Sudan
ABSTRACT
Finite element (FE) method is presented for the analysis of thin rectangular laminated
composite decks plates under the biaxial action of in – plane compressive loading. The
analysis uses the classical laminated plate theory (CLPT) which does not account for shear
deformations. In this theory it is assumed that the laminate is in a state of plane stress, the
individual lamina is linearly elastic, and there is perfect bonding between layers. The classical
laminated plate theory (CLPT), which is an extension of the classical plate theory (CPT)
assumes that normal to the mid – surface before deformation remains straight and normal to
the mid – surface after deformation. Therefore, this theory is only adequate for buckling
analysis of thin laminates. A Fortran program has been developed. New numerical results are
generated for in – plane compressive biaxial buckling which serve to quantify the effect of
boundary conditions on buckling loading. It is observed that, for all cases the buckling load
increases with the mode number but at different rates depending on whether the plate is simply
supported, clamped or clamped – simply supported. The buckling load is a minimum when
the plate is simply supported and a maximum when the plate is clamped. Because of the
rigidity of clamped boundary condition, the buckling load is higher than in simply supported
boundary condition. It is also observed that as the mode number increases, the plate needs
additional support.
Keywords: Boundary conditions, biaxial buckling, classical laminated plate theory, finite
element, Fortran program, composite laminated decks plates.
CONCLUSIONS
A Fortran program based on finite elements (FE) has been developed for buckling
analysis of thin rectangular laminated decks plates using classical laminated plate theory
(CLPT). The problem of buckling loads of generally layered composite plates has been
studied. The problem is analyzed and solved using the energy approach, which is formulated
by a finite element model. In this method, quadrilateral elements are applied utilizing a four
noded model. Each element has three degrees of freedom at each node. The degrees of
freedom are: lateral displacement ( ), and rotation ( ) and ( ) about the and axes
respectively. The finite element model has been formulated to compute the buckling loads of
laminated plates with rectangular cross – section and to study the effect of boundary
conditions on the non – dimensional critical buckling loads of laminated composite plates.
New results have been presented. It is observed that, for all cases the buckling load increases
with the mode number but at different rates depending on whether the plate is simply
supported, clamped or clamped – simply supported. The buckling load is a minimum when
the plate is simply supported and a maximum when the plate is clamped. Because of the
rigidity of clamped boundary condition, the buckling load is higher than in simply supported
boundary condition. It is also observed that as the mode number increases, the plate needs
additional support.
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