Title page for ETD etd-051199-082137

Type of Document Dissertation
Author Tiwari, Nachiketa
Author's Email Address ntiwari@vt.edu
URN etd-051199-082137
Title Secondary Buckling of Laminated Composite Plates
Degree PhD
Department Engineering Mechanics
Advisory Committee
Advisor Name Title
Hyer, Michael W. Committee Chair
Johnson, Eric R. Committee Member
Librescu, Liviu Committee Member
Plaut, Raymond H. Committee Member
Ragab, Saad A. Committee Member
  • snap through
  • secondary buckling
  • composites
  • boundary conditions
  • imperfections
Date of Defense 1999-05-03
Availability mixed


Nachiketa Tiwari

Michael W. Hyer, Chairman

Engineering Mechanics


The postbuckling load carrying capacity of composite plates offers

immense potential to their applications for loads exceeding their primary

buckling load. However, such an efficient and economical usage of these

plates can be reliable only if the nonlinear postbuckling behavior of

these plates, which includes a good understanding of secondary buckling,

is understood thoroughly. The present investigation is an attempt to

understand secondary buckling of almost square composite clamped-simply

supported plates, both unstiffened as well as stiffened, in some detail.

With the help of the finite element method, a large number of numerical

studies have been conducted to understand the secondary buckling

characteristics. The sensitivity of these characteristics to variations

in boundary conditions, lamination sequence, imperfections, and stiffener

geometry has been considered. It has been found that the occurrence of

secondary buckling in clamped-simply supported plates under uniform end

shortening critically depends on the intensity of restrictions imposed on

the inplane normal displacements along the unloaded simply supported

edges of the plate. These restrictions could be due to the actual

boundary conditions at these edges, or due to the presence of stiffeners

along these edges. It has also been found that the presence of

imperfections significantly delays the event of secondary buckling.

Finally, it has been found that changes in lamination sequence of the

plate alter its secondary buckling characteristics in ways that are, in

general, quantitative in nature. The numerical investigations were

followed by a limited number of experiments involving the testing of

unstiffened as well as stiffened composite plates with the intent of

augmenting the confidence in the numerical predictions made. Three

different lamination sequences were considered during the testing phase

of this investigation. It was found that the agreement between

experimental data and numerical predictions was quite good. The

occurrence of secondary buckling followed the predictions closely.

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