• Journal of Korean Society of Steel Construction
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• v.16 no.5 s.72
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• pp.621-628
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• 2004

This paper introduces a new theory, that in a stiffened plate, a steel stiffener could be substituted a composite material in order to prevent from buckling. Changing a steel stiffener into a composite material would not only preclude welding, but could also prevent damage to the material due to fatigue and corrosion.A composite material is assumed to adhere to a steel plate, and is never separated from the plate until the steel plate reaches buckling.Such plate has variable shapes, with different lengths and widths, and also shows an anisotropic material property. LUSAS, a commercial finite element analysis package, was used in the buckling analysis.This paper investigated buckling behavior in anisotropic composite plates with variable parameters.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.4
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• pp.328-338
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• 2007

One of main advantages of composite using smart material as reinforcement can be controlled cracks behavior inside the composite. If the smart composite is applied as part of the structure, the use of the shape memory effect of the smart material is the best way to protect the propagation of cracks generated in the structure while use. In this study, the optical manufacturing conditions for the smart composite were derived. In order to evaluate the shape memory effect by shape memory alloy, the tensile load was applied to the smart composite and stress distribution was inspected. And then, the smart composite was heated to a certain temperature and the shape memory alloy would shrink to the original shape. Finally, at this point the recovering status of stress using photoelastic instrument was discussed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.3
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• pp.117-127
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• 2012

As increasing number of large-size earthquake around Korean peninsula, many interests have been focused to the earthquake strengthening of existing structures. Fiber reinforced plastic composite material is one of strengthening material widely used to increase seismic performance of structures. It should have high stiffness as well as large ductility to provide best strengthening result. Thus selection of stiffener and fiber in composite is of important. In this study, the optimal combination of fiber and stiffener is selected with variety of tensile tests. In order to investigate performance of chosen composite material, several finite element analyses are performed with proposed FRP composite material for existing RC columns. It is discussed that the seismic performance of strengthened columns through the load-displacement relationship. It is shown that the proposed composite material can increase the strength as well as ductility of exiting RC columns.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.220-223
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• 2003

The methodology of micromechanical finite element method (MFEM) is proposed to calculate the micromechanical strains on fiber and matrix under mechanical and thermal loadings. For micromechanical analysis, composite structure is idealized the square and hexagonal unit cells. Boundary conditions are determined to calculate the effective material properties of composites and the strain magnification matrix. And they are verified by comparing with the results from multi cells, and the strain distributions of the unit cells are in accordance with those of the multi cells. Finally, the effective material properties of composite structure are obtained with respect to its fiber volume fraction and compared with results from rules-of-mixture.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.04a
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• pp.91-94
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• 1999

• Composites Research
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• v.19 no.2
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• pp.1-6
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• 2006

The civilian and military agencies require the use of statistic-based allowable to design aerospace vehicles with composite materials. In order to comply this regulation, it is necessary to establish relatively large amount of database, which increases test costs and time. Recently NASA/FAA developed the new method which can satisfy the regulation with smaller test matrix through AGATE(Advanced General Aviation Transport Experiments) program. Especially the concept of material equivalency is very useful when the material has been certified in previous program, and it allows the engineer to use the database with the addition of small test matrix. This paper summarizes the material equivalency and acceptance test methodology so that composite material database can be shared and improve the credibility of the material quality. As a demonstration, the material design allowable of the high temperature carbon/epoxy composite developed domestically was determined with this methodology.

• Journal of Ocean Engineering and Technology
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• v.7 no.1
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• pp.25-32
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• 1993

In composite materials, the fracture perpendicular to the fiber direction usually shows a non-linear behavior accompannying blunting and plastic deformation around the crack tip. In this study, the fracture thoughness in random short fiber SMC composite material and Carbon/Epoxy composite material is estimated by the A.M.(Area Method) and the G.L.M.(Generalized Locus Method) which can determine a stable total energy release rate(G$_T$) not only in highly elghly elastic material but also in highly non-linear materials.

• Composites Research
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• v.32 no.1
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• pp.13-20
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• 2019

In this study, in order to improve the quality issue and component characteristics of the battery module, which is one of the major parts of the electric vehicle. The structure is reinforced by using the composite material and the mechanism structure optimization of Hybrid concept which can overcome the disadvantages of single material was performed and the performance was compared. For this purpose, figure out the main design variables of composite materials according to Classical Laminated Plate Theory (CLPT) and the algorithm for predicting composite material properties have been studied. Based on the mechanical properties of the designed composite materials, finite element analysis (FEM) and the performance of the battery module was verified. Consequently, according to the verification result, Hybrid Battery Module reinforced with Selective Composite Patch can reduce the weight by 30% and reduce the product thickness by 32.5% compared with the existing Al battery module and proved the merit of Hybrid structure such as maintaining impact performance.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.183-188
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• 2002

Co-cured composite materials has its own characteristics, so its thermal expansion is different each other. The selection of tool material for co-cured composite part in high temperature more over $350^{circ}F$ and 50 Psi pressure have to consider part thermal expansion, size, shape, and economic aspect in production line. So it is important choose tooling material in manufacturing composite parts. We called the tool for airplane composite parts as BAJ (Bonding Assembly Jig). Composite parts are cured on the BAJ in autoclave. BAJ have to stable at high temperature over $350^{circ}F$ and 50 Psi pressure, Considering composite parts' dimensional tolerance compare to heat up in autoclave. This paper come from the results of the experiment at the composite parts production line and review other aircraft company's method for tooling This is for the engineer engaged in composite parts manufacturing.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.268-271
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• 2001

When compared to other composite materials such as FRP and MMC, hybrid composite material is more attractive one due to the high specific strength and the resistance to fatigue. However, the fracture mechanism of hybrid composite material is extremely complicated because of the bonding structure of metals and FRP. Recently, nondestructive technique has been used to evaluate the fracture mechanism of these composite materials. In this study, AE technique has been used to clarify the fracture mechanism and the degree of damage for Al 7075/CFRP hybrid composite material. It was found that AE event, energy and amplitude among AE parameters were effective to evaluate fracture process of Al 7075/CFRP composite material. In addition, the relationship between the AE signal and the characteristics of failure surface using optical microscope was discussed.