• Korean Journal of Metals and Materials
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• v.49 no.8
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• pp.589-595
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• 2011

Laminated glass fiber-reinforced plastic (GFRP) composites were applied to an insulating structure of a magnet system for a nuclear fusion device. Decreased inter-laminar strength by a strong repulsive force between coils which is induced a problem of structural integrity in laminated GFRPs. Therefore, it is important to investigate the inter-laminar characteristics of laminated GFRP composites in order to assure more reliable design and better structural integrity. Three types of the laminated GFRP composites using a high voltage insulating materials were fabricated according to each molding process. To evaluate the grade of the fabricated composites, mechanical tests, such as hardness, tensile and compressive tests,were carried out. The autoclave molding composites satisfied almost of the mechanical properties reguested at the G10 class standard, but the vacuum impregnation (VPI) and Prepreg composites did not.

• Steel and Composite Structures
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• v.9 no.5
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• pp.419-444
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• 2009

Flange and web local buckling in beam plastic hinge regions of steel moment frames can prevent beam-column connections from achieving adequate plastic rotations under earthquake-induced forces. Reducing the flange-web slenderness ratios (FSR/WSR) of beams is the most effective way in mitigating local member buckling as stipulated in the latest seismic design specifications. However, existing steel moment frame buildings with beams that lack the adequate slenderness ratios set forth for new buildings are vulnerable to local member buckling and thereby system-wise instability prior to reaching the required plastic rotation capacities specified for new buildings. This paper presents results from a research study investigating the cyclic behavior of steel I-beams modified by a welded haunch at the bottom flange and reinforced with glass fiber reinforced polymers at the plastic hinge region. Cantilever I-sections with a triangular haunch at the bottom flange and flange slenderness ratios higher then those stipulated in current design specifications were analyzed under reversed cyclic loading. Beam sections with different depth/width and flange/web slenderness ratios (FSR/WSR) were considered. The effect of GFRP thickness, width, and length on stabilizing plastic local buckling was investigated. The FEA results revealed that the contribution of GFRP strips to mitigation of local buckling increases with increasing depth/width ratio and decreasing FSR and WSR. Provided that the interfacial shear strength of the steel/GFRP bond surface is at least 15 MPa, GFRP reinforcement can enable deep beams with FSR of 8-9 and WSR below 55 to maintain plastic rotations in the order of 0.02 radians without experiencing any local buckling.

• Journal of Ocean Engineering and Technology
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• v.11 no.2
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• pp.48-56
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• 1997

This work has been investigated in order to study the influence of the moisture absorption on the mechanical pf the glass fiber/epoxy resein composites and the carbon fiber/epoxy resein composites. The types of glass fiber used in the glass fiber/epoxy resein composites were randomly oriented fiber and plain fabric fiber. And carbon fiber.epoxy resein composites was laminated with fabric prepreg which was formed with carbon fiber and epoxy resein. Both composites were immersed up to 100 days in distilled water at $80^{\circ}C$, and then dried up to 3 days in an oven at 80$80^{\circ}C$. Both composites were measured for the weight gain of water(wt.%) and tensile strength through immersion and dry time. Consequently, it was found that the tensile strength of thw glass fiber/epoxy resein composites and the carbon fiber/epoxy resein composites were reduced proportionally to the moisture absortion rate. Also, the tensile strength of glass fiber composites was decreased more than that of the carbon fiber composites. Additionally, it was found that the tensile strength of all composites which decreased by moisture absorption were partly recovered by drying in an oven at 80$80^{\circ}C$.

• Composites Research
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• v.36 no.1
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• pp.37-41
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• 2023

The treated water inside the ballast electrolytic cell creates a highly alkaline atmosphere due to hydroxide generated at the DSA(Dimension Stable Anode) electrode during electrolysis. In this study, a composite material that can replace the weakness of the PE-coated steel pipe used in the existing ballast pipe was prepared. The test samples are BRE(Basalt fiber reinforced epoxy), BRP(Basalt fiber reinforced unsaturated polyester), GRE(Glass fiber reinforced epoxy), and GRP(Glass fiber reinforced unsaturated polyester). And then it was immersed in NaOH for 720 hours. The friction test of each specimen was conducted. The Friction coefficient analysis according to material friction depth and interfacial adhesion behavior between resin and fiber were analyzed. As a result, the mechanism of interfacial separation between resin and fiber could be analyzed. In the case of the unsaturated polyester resin with low interfacial bonding strength the longer the immersion time in the alkaline solution, the faster the internal deterioration caused by the deterioration that started from the surface, resulting in a decrease in the friction coefficient. It is hoped that this study will help to understand the degradation behavior of composite materials immersed in various chemical solutions such as NaOH, acid, and sodium hypochlorite in the future.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.132-137
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• 2012

To enhance the CAE accuracy, the definition of material behavior is one of key influence on the result. In case of plastic material with fiber reinforcement, the anisotropic material behavior should be taken into account to increase of CAE accuracy. BASF has developed an innovative CAE tool, ULTRASIM$^R$, which is capable of generating material models of thermoplastic materials for structural simulation. ULTRASIM$^R$, not only the glass fiber orientation effect, but also the weld line effect, tensile-compression anisotropy, strain rate effect are combined in a non-linear material law, which will be evaluated in a unique failure criterion, thus resulting in an highly accurate CAE approach.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.669-675
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• 1997

This paper investigates the performances of GFRP bar and its possibility for using a substitute of steel bar. GFRO bar was made with introducing the glass fiber into GTR added UPE. We carried out the tensile test of GFRP and steel bar and out the three point bend test bond-test and fracture energy measurement on the GFRP bar and steel bar reinforced concrete. The GFRP bar was excellent as comparison with steel bar in the contribution to the energy absorption and the ductility of concrete. But its tensile, bond and bend strengthes were comparatively small. In order to improve these defects, we judged that glass fibers in GFRP bar must be completely adhesive one another by the impregnating glass fibers into UPE.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.2
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• pp.35-40
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• 2011

We have studied the impact and bending characteristics of a dual band antenna (1.575, 2.645 GHz) with composite sandwich construction. Mechanical performance of the antenna can be improved by reinforcing the antenna by sandwiching the planar antenna with layers of carbon fiber-reinforced plastic(CFRP) and glass fiber-reinforced plastic(GFRP) using an adhesive film. According to the ASTM D7137, ASTM C393 and MIL-STD401B, impact and bending test were performed and the S-parameters and gains of the antenna were measured in order to verify electrical and mechanical performance. The maximum contact load and the bending load of the antenna are 4 kN and 400 N and gains of the antenna are 6 dBi and 4.6 dBi in the GPS and DMB bands, respectively. The proposed antenna structure can be applied to surfaces of vehicles.

• Computers and Concrete
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• v.17 no.2
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• pp.215-225
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• 2016

High performance materials such as Fiber Reinforced Plastic (FRP) are often used for retrofitting structures against blast loads due to its ductility and strength. The effectiveness of retrofit materials needs to be precisely evaluated for the retrofitting design based on the dynamic material responses under blast loads. In this study, the blast resistance of Carbon Fiber Reinforced Plastic (CFRP) and Kevlar/Glass hybrid fabric (K/G) retrofitted reinforced concrete (RC) wall is analyzed by using the explicit analysis code LS-DYNA, which accommodates the high-strain rate dependent material models. Also, the retrofit effectiveness of FRP fabrics is evaluated by comparing the analysis results for non-retrofitted and retrofitted walls. The verification of the analysis is performed through comparisons with the previous experimental results.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.2
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• pp.115-123
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• 2007

For investigating self-diagnosis applicability, a method based on monitoring the changes in the electrical resistance of carbon fiber reinforced concrete has been tested. Then after examining change in the value of electrical resistance at each flexural weight-stage of carbon fiber in CFGFRP (carbon fiber and glass fiber reinforcing plastic) with new type rib and carbon sheet for concrete reinforcing, the correlations of electrical resistance and load as a function of strain, deflection were analyzed. As the results, it is clarified that when carbon fiber rod, rib and sheet fracture, the electrical resistance of it increase largely, and specially in case of CFGFRP, afterwards glass fiber tows can be resist the load due to the presence of the hybrid (carbon and glass) reinforced fiber. Therefore, it can be recognized that reinforcing bar and new type rib of CFGFRP and sheet of CF could be applied for self-diagnosis of fracture in reinforced FRP concrete.

• Composites Research
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• v.26 no.6
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• pp.380-385
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• 2013

Characteristics of delamination factor and surface roughness by drilling condition for glass fiber reinforced plastic (GFRP) composites were investigated in this paper. An expression to quantify the delamination factor was induced by using image pixels of the entry and the experimental drilling was accomplished by fabricating several GFRP specimens in condition of minimizing the effect of vibration and heat. A method for measuring 6 points average surface roughness was applied to acquire the more reliable roughness values. The experimental results showed that the delamination factor was decreased as the feed rate was increased and it was also slightly decreased as the cutting speed was increased. Also, it was investigated that the surface roughness at inner surface of drilled holes was increased as the feed rate was increased, whereas the roughness values were not affected by the cutting speed variation.