• Structural Engineering and Mechanics
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• v.27 no.2
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• pp.199-222
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• 2007

Composite laminated structures supported on elastic foundations are being increasingly used in a great variety of engineering applications. Composites exhibit larger dispersion in their material properties compared to the conventional materials due to large number of parameters associated with their manufacturing and fabrication processes. And also the dispersion in elastic foundation stiffness parameter is inherent due to inaccurate modeling and determination of elastic foundation properties in practice. For a better modeling of the material properties and foundation, these are treated as random variables. This paper deals with effects of randomness in material properties and foundation stiffness parameters on the free vibration response of laminated composite plate resting on an elastic foundation. A $C^0$ finite element method has been used for arriving at an eigen value problem. Higher order shear deformation theory has been used to model the displacement field. A mean centered first order perturbation technique has been employed to handle randomness in system properties for obtaining the stochastic characteristic of frequency response. It is observed that small amount of variations in random material properties and foundation stiffness parameters significantly affect the free vibration response of the laminated composite plate. The results have been compared with those available in the literature and an independent Monte Carlo simulation.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.9-12
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• 2001

Composite materials can be used economically and efficiently in broad civil engineering applications when standards and processes for analysis, design, fabrication, construction and quality control are established. Many of the bridge systems, including the girders and cross-beams, and concrete decks behave as the special othotropic plates. Such systems with boundary conditions other than Navier or Levy solution types, or with irregular cross sections, analytical solution is very difficult to obtain. Numerical method for eigenvalue problems are also very much involved in seeking such a solution. A method of calculating the natural frequency corresponding to the first mode of vibration of beam and tower structures with irregular cross-sections was developed and reported by the author in 1974 Recently, this method was extended to two dimensional problems including composite laminates, and has been applied to composite plates with various boundary conditions with/without shear deformation effects and reported at several international conferences including the Eighth Structures Congress of American Society of Civil Engineers in 1990. In this paper, the result of application of this method to the special orthotropic plates with various boundary condition is presented.

• Journal of Korean Society of Steel Construction
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• v.11 no.2 s.39
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• pp.117-129
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• 1999

The objective of this study is to identify the advantages of composite materials and to investigate the behavior of the anisotropic symmetric laminated cylindrical shell structures. To analyze the anisotropic symmetric laminated cylindrical shell structures, the finite difference technique. that consists of forward, central and backward difference, is introduced. In this study, the degree of freedom consists of three displacements and, especially, two moments except twisting moment. It has the advantage of improving the accuracy for calculating the moments. All four edges are assumed to be simply supported. From the numerical results, it is proved that the finite difference technique can be used efficiently to analyze the anisotropic symmetric laminated cylindrical shells and gives a guide in deciding how to make use of the fiber angle the anisotropic symmetric laminated cylindrical shells.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.69-72
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• 2004

A new three-node triangular shell element based on higher order zig-zag theory is developed for laminated composite shells with multiple delaminations. The present higher order zig-zag shell theory is described in a general curvilinear coordinate system and in general tensor notation. All the complicated curvatures of surface including twisting curvatures can be described in an exact manner in the present shell element because this element is based on geometrically exact surface representation. The displacement field of the proposed finite element includes slope of deflection, which requires continuity between element interfaces. Thus the nonconforming shape function of Specht's three-node triangular plate bending element is employed to interpolate out-of-plane displacement. The present element passes the bending and twisting patch tests in flat surface configurations. The developed element is evaluated through the eigenvalue problems of composite cylindrical shells with multiple delaminations. Through the numerical examples it is demonstrated that the proposed shell element is efficient because it has minimal degrees of freedom per node. The present shell element should serve as a powerful tool in the prediction of natural frequency and modes of multi-layered thick laminated shell structures with arbitrary-shaped multiple delaminations.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.193-196
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• 2001

The purpose of this study is the design of composite shaft which is wound by Filament Winding method. Classical laminated plate theory was used for analyzing the stress, and for structure design. The diameter and thickness of composite shaft were calculated by this theory. The result that if tensile stress was zero, torsion stress was a certain value below 0.4(diameter rate) and torsion strength was the highest value on $45^{\circ}C$(winding angle). In case of $90^{\circ}C$(winding angle), we have to consider the torsional monent when the composites shaft was load.

• Journal of the Korean Society of Safety
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• v.16 no.4
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• pp.128-133
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• 2001

In this paper, stability analysis is carried out far the out of plane behaviors under compressive loads to the conical direction. It is not easy to obtain the analytic solutions about the stability analysis of anisotropic conical shells consisted of composite materials. For solving this problems, this paper used the finite difference method which is one of the numerical methods. The characteristics of the buckling behaviors of anisotropic laminated composite conical shells may be different according to a variety of causes, that is, the change of fiber angle, material arrangement, radius ratio, shape ratio and so on. The objective of this study is to analyze buckling behaviors of circular conical shells with shear deformation effects and to prove the advantage of composite materials.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.169-172
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• 2000

Although extensive efforts have been devoted to the optimal design of composite laminated plates in recent years, some practical issues still need further research. One of them is the handling of the uncertainties in material properties, which were ignored in most researches in the past. In this paper, the convex modeling is used in calculating the failure criterion, given as constraint, to consider the uncertain material properties in the thickness optimization. Numerical results show that the optimal thickness increases when the uncertainties of elastic moduli considered, which shows such uncertainties should not be ignored for safe and reliable designs.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.9
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• pp.68-74
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• 1998

The ESPI(Electronic Speckle Pattern Interferometry) is a real time, full-field, non-destructive optical measurement technique that allows static and dynamic deformation analysis and surface shape measurements of engineering structures. e .g. turbine blades. vehicle engine components, body panels, etc. This technique is very similar to holographic interferometry, but uses a solid static camera and an image processing board for recording and digital processing of speckle patterns. In this paper it is presented that FEM results for the free vibration of symmetrically laminated composite as [30/-30/90]s. The natural frequencies of laminated composite rectangular plates having the particular boundary condition are experimentally obtained. In order to demonstrate the validity of the experiment, FEM analysis using ANSYS was performed and natural frequencies experimentally obtained is compared with calculation by FEM analysis. The results obtained from both experiment and FEM analysis show a good agreement.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.123-126
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• 2004

Two-way shape memory effect(TWSME) under residual stresses are considered in the present study. The structure using two-way shape memory effect concept returns to its initial shape by increasing or decreasing temperature under the initially given residual stress. In the present study, we use a thermo-mechanical constitutive equation of SMA and laminated composite beam are considered as simple morphing structural components which are based on large deformable 2D composite beam theory. Numerical results of fully coupled SMA-composite structures are presented.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.46-49
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• 2000

A decoupled thermo-~lezoelectric-mechanical model of composite laminates with surface bonded piezoelectric actuators, subjected to externally applied load, temperature change load, electric field load is developed. The governing differential equations are obtained by applying the principle of free energy and variational techniques. A higher order zigzag theory displacement field is employed to accurately capture the transverse shear and normal effects in laminated composite plates of arbitrary thickness.