• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.54-59
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• 2001

This paper presents an analytical investigation pertaining to the elastic buckling behavior of pultruded fiber reinforced plastic equal-leg angle members under concentric axial compression. The elastic local and global buckling (flexural, torsional, and flexural-torsional) analyses are conducted, respectively, and the analytical results are compared with the existing experimental results. The differences were more than 10%, and the experimental results were higher than the analytical results.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.91-94
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• 2001

This paper presents the analytical investigation pertaining to the local buckling behavior of orthotropic channel section compression members stiffened with unsymmetric stiffeners at its free edges. In the analysis, tile edge stiffener is modeled as a beam element or a plate element. The result of both cases is presented in graphical form so that the effects of edge stiffeners on the local buckling strength of edge stiffened channel section member can be found.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.5-8
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• 2000

This paper presents the analytical investigation pertaining to the local buckling behavior of orthotropic open section thin-walled compression members with asymmetric edge stiffeners. In the analysis, 3 different cases of the second moment of inertia are considered to find the asymmetric edge stiffener effect on the local buckling strength. The analytical study results are presented in the graphical form so that the edge stiffener effects on the local buckling strength can be easily found.

• Journal of the Korean Geotechnical Society
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• v.23 no.3
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• pp.77-88
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• 2007

A micromechanics-based model to simulate the elastic and elastic-plastic behavior of granular soils is developed. The model accounts for the fabric anisotropy represented by the statistical parameter of the spatial distribution of contact normals, the evolution of fabric anisotropy as a function of stress ratio, the continuous change of the co-ordination number relating to the void ratio, and the elastic and elastic-plastic microscopic contact stiffness. Using the experimental data for metallic materials, the elastic-plastic contact stiffness is derived as a power function of the normal contact force as well as the contact force initiating the yielding of contact bodies. To quantitatively assess microscopic model parameters, approximate solutions of cross-anisotropic elastic moduli are derived in terms of the micromechanical parameters.

• Journal of Korean Society of Steel Construction
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• v.18 no.1
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• pp.93-100
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• 2006

A simple but precise method of calculating the natural vibration frequencies of composite laminated plates with all-simple support and under axial loadings is presented herein. This method uses deflection influence surfaces, which can be obtained by any method for vibration analysis and member due to the inertia force under resonance condition. Beginning with an initially guessed mode shape, the exact mode shape is obtained by the process similar to iteration. In this paper, equations are given for the case of special orthotropic laminates. The same equations, however, can be used for any laminate as long as ${B_1_6}$, ${B_2_6}$, ${D_1_6}$, and ${D_2_6}$ are negligible as the number of plies increases. Some laminates that possess such properties are presented in the paper.

• Composites Research
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• v.22 no.5
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• pp.24-29
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• 2009

In this paper, a post-tensioned reinforced concrete slab was analyzed by the specially orthotropic laminates theory. Both the geometrical and material property of the cross section of the slab was considered symmetrically with respect to the neutral surface so that the bending extension coupling stiffness, $B_{ij}=0$, and $D_{16}=D_{26}=0$. Reinforced concrete slab behave as specially orthotropic plates. In general, the analytical solution for such complex systems is very difficult to obtain. Thus, finite difference method was used for analysis of the problem. In this paper, the finite difference method and the beam theory were used for analysis. The result of beam analysis was modified to obtain the solution of the plate analysis.

• Journal of Korean Society of Steel Construction
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• v.18 no.2
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• pp.161-171
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• 2006

paper presents the results of a three-dimensional study of the natural vibration of laminated composite rectangular plates with various combinations of clamped and free boundaries. The Ritz method was used to obtain the stationary values of the associated Lagrangian, with displacements approximated using mathematicaly complete, characteristic orthogonal polynomials. The correctness of the three-dimensional model was established through a convergence study of the non-dimensional frequencies, followed by a comparison of the analytical findings in the existing literature. The wide scope of additional three-dimensional frequency results explains the influence of a number of geometrical and material parameters for angle-ply and cross-ply laminated plates, namely aspect ratio (${\mathcal{a/b}}$), thickness ratio (${\mathcal{a/h}}$), orthotropy of material, number of plies (${\mathcal{N}}$), fiber orientation angle (${\theta}$), and stacking sequence.

• Composites Research
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• v.14 no.6
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• pp.38-46
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• 2001

In this study, An optimization code that can design microwave absorbing composite laminates is developed, and 3-layered microwave absorbing composite laminates are developed by optimizing the thickness of each layer. The layers are 3 different composite laminates. Many variables including lay-up angles of electromagnetically orthotropic composite layer can be considered in this code. The developed laminate is composed of an impedance matching layer of glass/epoxy fabric laminate, a glass/epoxy fabric laminate layer containing aluminum filler and carbon/epoxy fabric laminate layer. Permittivities of the materials are obtained using a network analyzer and a coaxial air line.

• Journal of Korean Society of Steel Construction
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• v.18 no.6
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• pp.737-746
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• 2006

The elastic buckling strength of a Glass Fiber Reinforced Plastic (GFRP) pipe reinforced with ribs was evaluated. The height and thickness of a rib and the spacing between two adjacent ribs were considered as factors affecting the buckling strength of the pipe. And also, the ratio of the longitudinal stiffness and transverse stiffness was considered as the parameter affecting the buckling strength as the GFRP is orthotropic material. Buckling strengths of various GFRP pipe models with different shapes and stiffness ratios were evaluated by FE analyses and a formula to estimate the elastic buckling strength of a rib-reinforced pipe made of orthotropic material was suggested from the regression with the results from the FE analysis. Analytical results show that a rib-reinforced pipe has a buckling strength superior to a general flat pipe and the suggested formula estimates accurate buckling strength of the rib-reinforced pipe.

• Composites Research
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• v.20 no.3
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• pp.43-49
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• 2007

Dynamic instability of rotating disks is the most significant factor to limit its rotating speed. Application of composite materials to rotating disks may enhance the dynamic stability leading to a possible design of rotating disks with lightweight and high speed. Whereas much work has been done on the effect of transverse shear and rotary inertia, called Timoshenko effect, on the dynamic behavior of plates, there is little work on the correlation between the effect and the rotation of disk, especially nothing in case of composite disks. The dynamic equations of a rotating composite disk are formulated with the Timoshenko effect and the vibrational analysis is performed by using a commercial package MSC/NASTRAN. According to the results, the Timoshenko effect goes seesaw in some modes, unlike the well-known fact that the effect decreases as the rotating speed increases. And it can be concluded, based only on the present results, that decrement of the Timoshenko effect by disk rotation grows larger as the thickness ratio decreases, the diameter ratio increases, the modulus ratio increases, and the mode number increases.