• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.7
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• pp.1244-1254
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• 1992

This paper investigates the vibrational damping characteristics of laminated plates composed of elastic, viscoelastic and elastic layers by theoretical and experimental methods. Laminated plates are in cylindrical bending and visco-elastic adhesive layer is assumed as the visco-elastic spring which takes damping effect through both shear and normal deformations. Governing equations oof laminated plates are derived in the form of simultaneous first order differential equations, which account for the longitudinal displacements, rotary inertia and shear deformations of elastic base plate and elastic constraining plate. The numerical calculations of the equations are illustrated by the applications to the cantilever beam in transverse vibration. The results of the solutions agree well with the experimental measurements in general. The damping effects due to the shear and thickness deformations in the adhesives are analyzed and it is shown that for thicker adhesives, the damping effect due to thickness deformation becomes significant and for thinner adhesives, due to shear deformation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.2002-2014
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• 1991

A refined two-dimensional analysis method, taking into account the crack opening deformation, is proposed for the evaluation of stress distributions in transverse cracked cross-ply laminates. The interlaminar stresses which play an important role in laminate failure are evaluated using the concept of interface layer. A series expansion of the displacements is employed and the thermal residual stresses and Poisson's effects in the laminated are taken into consideration in the formulation. The stress distributions are compared with finite element results. The proposed method represents well the characteristics of the stress distributions. The through-the-thickness variation of the stress distribution is remarkable near the transverse crack due to the crack opening deformation. The interlaminar stresses have significant values at the transverse crack tip and the proposed analysis can be applied as a basis for the prediction of the induced delamination onset by using appropriate failure criteria.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.4
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• pp.461-466
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• 2013

Advanced fiber-reinforced laminated composites are widely used in various fields of engineering to reduce weight. The material property of each ply is well known; specifically, it is known that ply is less reliable than metallic materials and very sensitive to the loading direction. Therefore, it is important to consider this uncertainty in the design of laminated composites. In this study, reliability analysis is conducted using COMSOL and MATLAB interactions for a laminated composite plate for the case in which the tip deflection is the design requirement and the material property is a random variable. Furthermore, the efficiency and accuracy of the approximation method is identified, and a probabilistic sensitivity analysis is conducted. As a result, we can prove the applicability of the advanced design method for the stabilizer of an underwater vehicle.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.5199-5206
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• 2010

In this paper, we investigate the buckling analysis of laminated composite plates, using a improved assumed natural strain shell element. In order to overcome membrane and shear locking phenomena, the assumed natural strain method is used. The eigenvalues of the laminated composite plates are calculated by varying the width-thickness ratio and angle of fiber. To improve an shell element for buckling analysis, the new combination of sampling points for assumed natural strain method was applied and the refined first-order shear deformation theory which allows the shear deformation without shear correction factor. In order to validate the present solutions, the reference solutions are used and discussed. The results of laminated composite plates under the in-plane shear loading may be the benchmark test for the buckling analysis.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.3
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• pp.267-275
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• 2009

This paper presents the p-convergent coupling element on the basis of the ESSE(equivalent single layer shell element) and the PLLE(partial-linear layerwise element) to analyze laminated composite plates. The ESSE is formulated by the degenerated shell theory, on the other hand, the assumption of the PLLE is piecewise linear variation of the in-plane displacement and a constant value of lateral displacement across the thickness. The proposed finite element model is based on p-convergence approach. The integrals of Legendre polynomials and Gauss-Lobatto technique are chosen to interpolate displacement fields and to implement numerical quadrature, respectively. This study has been focused on the verification of p-convergent element. For this purpose, various finite element multiple models associated with the combination of ESSE and PLLE elements are tested to show numerical stability. The simple examples such as a cantilever beam subjected vertical load and a plate with tension are adopted to evaluate the performance of proposed element.

• Applied Microscopy
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• v.25 no.3
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• pp.75-81
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• 1995

The microstructural characterization of ternary $ZnS_{x}Se_{1-x}$(x=0.085) on GaAs(001) substrate grown up to $2{\mu}m\;at\;300^{\circ}C$ by molecular beam epitaxy(MBE) which has a single growth chamber was investigated by high resolution transmission electron microscope (HRTEM) working at 300 kV with point resolution of 0.18nm. The interface in the ZnSSe/GaAs specimen maintains a pseudomorphism with the substrate, but the epilayer has high density of stacking faults and moire fringes. The pits which had formed along <111> direction were found at the interface of ZnSSe/GaAs. The pits were responsible for producing defects in both epilayer and substrate. The wavy interface which has the difference of 15nm in height was found to maintain the pseudomorphism with the substrate and no stacking faults were found around the interface. However there exists faint and fine moire fringes in the epilayer near interface.

• Journal of Korean Society of Steel Construction
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• v.14 no.1
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• pp.105-111
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• 2002

A post-tensioned slab bridge is analyzed by the specially orthotropic laminates theory. Both the geometry and the material of the cross section of the slab are considered symmetrical with respect to the mid-surface so that the bending extension coupling stiffness, $B_{ij}=0$, and $D_{16}=D_{26}=0$. Each longitudinal and transverse steel layer is regarded as a lamina, and material constants of each lamina is calculated by the use of rule of mixture. This bridge with simple support is under uniformly distributed vertical and axial loads. In this paper, the finite difference method and the beam theory are used for analysis. The result of beam analysis is modified to obtain the solution of the plate analysis. The result of this paper can be used for post-tensioned slab bridge analysis by the engineers with undergraduate study in near future.

• Magazine of the Korea Concrete Institute
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• v.11 no.1
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• pp.119-127
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• 1999

The objective of this study is to simulate the fracture behavior of composite structure bonded with more than 2 different cementitious materials. For this, concrete and cement were stacked and bonded in a direction perpendicular to loading and specimens were tested. Each constituent material of concrete and cement was fabricated independently also, and three point bending and indirect tensile tests were carried out for the acquisition of measured values applicable to the proposed model. As a result of comparing theoretical results and experimental ones, it was found that the proposed model derived from fictitious crack theory can be used to predict the fracture behavior of composite structures on the vases of well agreement with experimental results. It was also noted that the degree of improvement of fracture energies and strengths is greatly dependent on the stacking sequence of layers composing of a composite structure. Thus, it can be concluded that brittleness or ductility of a composite structure can be accomplished by a proper arrangement of layers on one's purpose throughout the proposed analysis.

• Composites Research
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• v.16 no.2
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• pp.33-40
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• 2003

In order to overcome one of the most pronounced shortcomings of conventional laminated composites, such as the low damage tolerance due to delamination, the thermoplastic materials and 3D (three-dimensional) preforms have been utilized in the manufacture of composite materials. From the newly developed process termed as the co-braiding, hybrid yarns of the thermoplastic fibers (PEEK) and reinforcing fibers (carbon) have been fabricated. In order to further enhance the delamination suppression, through thickness fibers have been introduced by way of 3D weaving technique in the fabrication of textile preforms. The preforms have been thermoformed to make composite materials. Complete impregnation of the PEEK into the carbon fiber bundles has been confirmed. For the comparison of mechanical performance of 3D woven composites, quasi-isotropic laminates using APC-2/AS4 tapes have been fabricated. Tensile and compressive properties of both the composites have been determined. Furthermore. the open hole, impact and CAI(Compression After Impact) tests were also carried out to assess the applicability of 3D woven textile reinforced thermoplastic composites in aerospace structures.

• Polymer(Korea)
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• v.24 no.6
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• pp.860-868
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• 2000

In this work, the electro-magnetic interference (EMI) characteristics of PAN-based carbon fibers-reinforced composites are investigated with difference to manufactural parameters, i.e., fiber grade, fiber orientation angle, and laminating method. As a result, EMI shielding effectiveness (SE) of the composites greatly depends on a fiber orientation in composite angle. Especially, the fiber grade affects SE of composites in case of orientation angle of 0$^{\circ}$. Then the SE become greater as the change of electric character according to the arrangement directions, i.e., electrical anisotropy in the same constituent materials. This is due to the skin effect which is represented in the surface of electro-magnetic wave in high-frequency range. In all cases according to lamination methods, the composites represents SE of 83~98% over. Whereas, in symmetric and unsymmetric laminate structures, the SE decreases slightly as the laminate angles of composites increases. On the contrary. the repeating laminates structure shows the opposite tendency. Especially, 90$^{\circ}$ repeating laminate structure shows the SE more than 90% over the measuring frequency.