• Composites Research
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• v.12 no.3
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• pp.45-54
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• 1999

In this paper, an experimental study on the buckling and postbuckling control of a laminated composite beam with eccentrically embedded SMA wire actuators is performed. For the purpose of enhancing the critical buckling load, buckling control is investigated through the use of reactive moment associated with the shape recovery force of SMA wire actuators. To improve the control authority for the buckling and postbuckling control of the SMA-composite beam, closed-loop control is used. The buckling and postbuckling control behaviours are presented and discussed qualitatively and quantitatively on loaddeflection plots considering the stacking sequence of the laminate, slenderness ratio of the beam and activation conditions of the SMA wire actuators. By maintaining the desired deflection shape with the proper reactive moment, buckling control can be extended to the postbuckling of the SMA-composite beam subjected to an external load.

• Structural Engineering and Mechanics
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• v.18 no.1
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• pp.41-58
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• 2004

The postbuckling behaviour of thin shells has fascinated researchers because the theoretical prediction and their experimental verification are often different. In reality, shell panels possess small imperfections and these can cause large reduction in static buckling strength. This is more relevant in thin laminated composite shells. To study the postbuckling behaviour of thin, imperfect laminated composite shells using finite elements, explicit incremental or secant matrices have been presented in this paper. These incremental matrices which are derived using Marguerre's shallow shell theory can be used in combination with any thin plate/shell finite element (Classical Laminated Plate Theory - CLPT) and can be easily extended to the First Order Shear deformation Theory (FOST). The advantage of the present formulation is that it involves no numerical approximation in forming total potential energy of the shell during large deformations as opposed to earlier approximate formulations published in the literature. The initial imperfection in shells could be modeled by simply adjusting the ordinate of the shell forms. The present formulation is very easy to implement in any existing finite element codes. The secant matrices presented in this paper are shown to be very accurate in tracing the postbuckling behaviour of thin isotropic and laminated composite shells with general initial imperfections.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.958-966
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• 1994

The postbuckling compressive strengths of $[0/90/\pm\theta]_s$ composite laminated cylindrical panels with various fiber angles and width-to-length ratios are characterized by the nonlinear finite element method. For the iteration and load-increment along the postbuckling equilibrium path a modified arc-length method in which the effect of failure can be considered is introduced. In the progressive failure analysis the maximum stress criterion and complete unloading model are used. Present finite element results show good agreement with experiments for $[0_3/90]_s$ cylindrical panel and $[0/\pm45/90/]_s$ plate. The postbuckling compressive strength of $[0/90/\pm\theta]_s$ composite laminated cylindrical panel is independent of the initial buckling stress but high in the panel with large value of the bending stiffness in axial direction. In the several cylindrical panels, it is observed that the prebuckling compressive failures occur and result into the collapse before the buckling.

• Steel and Composite Structures
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• v.26 no.1
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• pp.17-29
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• 2018

The thermal effects on the buckling, postbuckling and nonlinear vibration behaviors of composite laminated trapezoidal plates are studied. Aiming at the complex plate structure and to simulate the temperature distribution of the plate, a finite element method (FEM) is applied in this paper. In the temperature model, based on the thermal diffusion equation, the Galerkin's method is employed to establish the temperature equation of the composite laminated trapezoidal plate. The geometrical nonlinearity of the plate is considered by using the von Karman large deformation theory, and combining the thermal model and aeroelastic model, Hamilton's principle is employed to establish the thermoelastic equation of motion of the composite laminated trapezoidal plate. The thermal buckling and postbuckling of the composite laminated rectangular plate are analyzed to verify the validity and correctness of the present methodology by comparing with the results reported in the literature. Moreover, the effects of the temperature with the ply-angle on the thermal buckling and postbuckling of the composite laminated trapezoidal plates are studied, the thermal effects on the nonlinear vibration behaviors of the composite laminated trapezoidal plates are discussed, and the frequency-response curves are also presented for the different temperatures and ply angles.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.288-291
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• 2004

The characteristics of the buckling analysis module for stiffened composite structures were studied in this paper. Composite stiffened structures have geometrical asymmetry and material properties asymmetry. Due to these reason, postbuckling analysis was essential and the characteristics of postbuckling analysis modules for ABAQUS were researched. Static analysis module was considered. By considering the material nonlinearity, progressive failure mechanism was applied and buckling strength was estimated

• Journal of the Korean Society for Precision Engineering
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• v.17 no.4
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• pp.163-172
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• 2000

The postbuckling behavior and progressive damage of composite laminated cylindrical shell under uniform external pressure were investigated by nonlinear finite element method programming. For the finite element analysis, nine-node 3-D degenerated elements were utilized, and arc-length method including line search was adopted for the iteration and load-increment along postbuckling equilibrium path. As results. buckling load, postbucking behavior, and progressive failure f3r various composite laminated cylindrical shells were discussed.

• Structural Engineering and Mechanics
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• v.56 no.1
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• pp.85-106
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• 2015

Postbuckling of thick plates made of functionally graded material (FGM) subjected to in-plane compressive, thermal and thermomechanical loads is investigated in this work. It is assumed that the plate is in contact with a Pasternak-type elastic foundation during deformation. Thermomechanical non-homogeneous properties are considered to be temperature independent, and graded smoothly by the distribution of power law across the thickness in the thickness in terms of the volume fractions of constituents. By employing the higher order shear deformation plate theory together the non-linear von-Karman strain-displacement relations, the equilibrium and compatibility equations of imperfect FGM plates are derived. The Galerkin technique is used to determine the buckling loads and postbuckling equilibrium paths for simply supported plates. Numerical examples are presented to show the influences of power law index, foundation stiffness and imperfection on the buckling and postbuckling loading capacity of the plates.

• Structural Engineering and Mechanics
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• v.6 no.6
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• pp.643-658
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• 1998

A thermal postbuckling analysis is presented for a moderately thick rectangular plate subjected to uniform or nonuniform tent-like temperature loading and resting on an elastic foundation. The plate is assumed to be simply supported on its two opposite edges and the two side edges remain free. The initial geometrical imperfection of the plate is taken into account. The formulation are based on the Reissner-Mindlin plate theory considering the first order shear deformation effect, and including plate-foundation interaction and thermal effects. The analysis uses a mixed Galerkin-perturbation technique to determine the thermal buckling loads and postbuckling equilibrium paths. Numerical examples are presented that relate to the performances of perfect and imperfect, moderately thick plates resting on Pasternak-type or softening nonlinear elastic foundations from which results for Winker elastic foundations follow as a limiting case. Typical results are presented in dimensionless graphical form.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.2
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• pp.354-362
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• 1995

The finite element modeling is used to study the buckling and postbuckling behavior of composite laminates with an embedded delamination. Degenerated shell element and rigid beam element are utilized for the finite element modeling. In the nonlinear finite element formulation, the updated Lagrangian description method based on the second Piola-Kirchhoff stress tensor and the Green strain tensor is used. The buckling and postbuckling behavior of composite laminates with a delamination are investigated for various delamination sizes, stacking sequences, and boundary conditions. It is shown that the buckling load and postbuckling behavior of composite laminates depend on the buckling model which is determined by the delamination size, stacking sequence and boundary condition. Also, results show that introduction of couplings can reduce greatly the buckling load.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.913-919
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• 2001

In this study, fiber orientation of stiffener was conducted to increase buckling load or failure load in each case with a different design value and a different objective function for stiffened laminated composite panel of I-type under compression loading. Regarding each of buckling load or failure load as objective function, optimum design was carried out. In respect of optimum design, it was investigated that optimum shape for buckling could improve fail load for postbuckling, because it was difficult to investigate the optimization of postbuckling which need long analysis times for nonlinear analysis.