• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.2
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• pp.61-69
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• 2011

Fiber Reinforced Plastic (FRP) sheets have been widely used to retrofit and rehabilitate RC structures, while in case of retrofitting steel structures, there are no codes and researches. It stems from configuration of member and characteristics of bonding behavior. This study focused on the static behavior of steel beams reinforcement by AFRP sheets. The main objective of the experimental programme was the evaluation of the force transfer mechanism, the increment of the beam load carrying capacity and the bending stiffness. A bending test was conducted on a H-shaped steel beam, with aramid FRP sheets bonded to its flanges. The mid-span deflection and the strain from three points along AFRP sheets were recorded Test results exhibit that the increment of the load-carrying capacity with reference to a mid-span deflection level of 15 mm(1/125mm of the clear span) was equal to 9.4% and for the two layers case, an elastic stiffness increment is slightly higher than one layer case.

• Journal of the Korean Institute of Gas
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• v.16 no.2
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• pp.25-30
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• 2012

This paper presents a stress safety of a composite pressure cylinder in which is composed of an aluminum liner and composite layers with carbon fiber/epoxy and glass fiber/epoxy resigns. The composite pressure cylinder for a hydrogen gas vehicle contains 9.2 liter hydrogen gas, and hydrogen gases are compressed by a filling pressure of 35MPa. The FEM computed results are analyzed based on the US DOT-CFFC basic requirement for a hydrogen gas cylinder and KS B ISO specification. The FEM results indicate that the stress, 247MPa of an aluminum liner is sufficiently low compared with that of 272MPa, which is 95% level of a yield stress for aluminum. And, the carbon fiber composite layers in which are wound on the surface of an aluminum cylinder are safe because the maximum carbon fiber stresses from 29.43% to 28.87% in hoop and helical directions are below 30% for a given minimum required burst pressure level, respectively. The carbon fiber composite layers are also safe because the stress ratios from 3.40 to 3.46 in hoop and helical directions are above 2.4 for a minimum safety level, respectively.

• Membrane Journal
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• v.31 no.2
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• pp.153-159
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• 2021

In recent years, polymer membranes, which are actively used in various industrial fields, have the advantage of being able to impart unique properties through the control of chemical structures and physical properties in the film-fabrication process, as well as through fabricating blend membranes mixed with various materials. In this study, the solubility parameter, which can be used as an index of miscibility with other materials, was calculated using molecular dynamics using a silkworm (Bombyx mori) silk polymer which has a wide potential to be used as an eco-friendly natural material. When the solubility parameter of polyvinylalcohol (PVA), which is also environmentally friendly and biocompatible, was calculated by molecular dynamics and compared with each other, it was confirmed that the two polymer materials had similar solubility parameter values. In conclusion, it was theoretically proved that the two polymers could blend well with each other, which was confirmed through experiments.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.631-635
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• 2011

Spherical and non-spherical silica particles prepared by the direct oxidation were studied for the effect of the particle size and shape of these particles on oxide CMP removal rate. Spherical silica particles, which have 10~100 nm in size, were prepared by the direct oxidation process from silicon in the presence of alkali catalyst. The 10 nm silica particles were aggregated by addition of an acid, an alcohol, or a silane as an aggregation inducer between the particles. Two or more aggregated silica particles were used as a seed to grow non spherical silica particles in the direct oxidation process of silicon in the presence of alkali catalyst. The oxide removal rate of spherical silica particles increased with increasing an average particle size for spherical silica abrasives in the oxide CMP. It further increased non-spherical particles, compared with the spherical particles in the similar average particle size.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.3
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• pp.89-95
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• 2022

In this study, glassy carbon coating was performed on the graphite using a phenolic resin and a curing agent was mixed with ethylene glycol as an additive to form the uniform surface. The phenolic resin was dried and cured under the environments of hot air, then converted into a glassy carbon layer by pyrolysis at 500~1,500℃. FTIR, XRD, SEM analysis, and density/porosity/contact angle measurement were performed for characterization of glassy carbon. The pyrolysis temperature for high-quality glassy carbon was optimized to be about 1,000℃. As the content of the additive increased, the effect of reducing surface defects on the coated surface, reduction of porosity, increase of contact angle, and increase of density were investigated in this study. The method of forming a glassy carbon coating layer through an additive is expected to be applicable to graphite coating and other fields.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5A
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• pp.519-529
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• 2009

Fiber reinforced composite materials have various advantages in mechanical and chemical aspects. Not only high fatigue and chemical resistance, but also high specific strength and stiffness are attained, and therefore, damping characteristics are beneficial to marine piles. Since piles used for marine structures are subjected to compression and bending as well, detailed research is necessary. Current study examine the mechanical behavior under flexural and/or compressive loads using concrete filled fiber reinforced plastic composite piles, which include large size diameter. 25 pile specimens which have various size of diameters and lengths were fabricated using hand lay-up or filament winding method to see the effect of fabrication method. The inner diameters of test specimens ranged from 165 mm to 600 mm, and the lengths of test specimens ranged from 1,350 mm to 8,000 mm. The strengths of the fill-in concrete were 27 and 40 MPa. Fiber volumes used in circumferential and axial directions are varied in order to see the difference. For some tubes, spiral inner grooves were fabricated to reduce shear deformation between concrete and tube. It was observed that the piles made using filament winding method showed higher flexural stiffness than those made using hand lay-up. The flexural stiffness of piles decreases from the early loading stage, and this phenomenon does not disappear even when the inner spiral grooves were introduced. It means that the relative shear deformation between the concrete and tube wasn't able to be removed.

• Journal of the KSME
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• v.32 no.1
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• pp.18-27
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• 1992

섬유강화 플라스틱을 시초로 복합재료가 상업적으로 생산, 판매되기 시작한지 어언 30여년이 되었다. 뛰어난 기계적 . 화학적 특성을 바탕으로 오늘날 복합재료는 신소재의 한 분야로 굳게 자리잡고 있다. 설계, 성형, 분석기술의 발전과 아울러 유리섬유 복합재료 이후에 특성이 뛰어난 복합재료 소재들이 개발되고 있어 복합재료의 응용범위를 더욱더 넓히고 있다. Boron, carbon, aramid섬유의 개발은 첨단 복합재료의 개발을 가능케 했으며 군용, 우주기기의 개발로 얻어진 결과들은 민간 항공기 또는 스포츠, 레저 분야에 많이 이용되고 있다. 민간 항공기의 많은 부분에 첨단 복합재료로 된 부품들이 사용되고 있으며 복합재료로된 골프채, 낚시대, 테니스채 그리고 스키 등을 우리 주변에서 손쉽게 찾아볼 수 있다. 이 글에서는 고분자 기지 복합재료를 중심으로 그 성형법 및 응용에 대하여 논하고 기타 특수용도 복합재료에 대해서 약술하고자 한다.

• Composites Research
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• v.34 no.1
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• pp.1-7
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• 2021

Fiber-reinforced thermoplastic composites are applied to transport industries to lightweight of body, and applications will be expanded gradually. In this study, the impregnation and mechanical properties of continuous glass fiber (GF) reinforced polycarbonate (PC) composites were evaluated with different molecular weights of PC. The continuous GF reinforced PC composite were prepared by using GF fabric and PC film via continuous compression molding method. The melting flow index and tensile strength of PC matrix were evaluated with different molecular weights. Mechanical properties (tensile, flexural, and compressive) and pore rate of GF/PC composite were evaluated with different molecular weights of PC. The fracture behavior was analyzed to fracture surface of GF/PC composite using FE-SEM images. As these results, it was condition of representing the best mechanical property that the GF/PC composite was prepared by using PC of 20,000 g/mol as matrix.

• Korean Chemical Engineering Research
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• v.45 no.5
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• pp.415-423
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• 2007

Photocatalytic water splitting (PWS) is the most promising technology to produce $H_2$ energy directly from renewable water and solar light. In spite of the remarkable progress made in the last decade, there are still many technical challenges remaining particularly in finding new photocatalytic materials with high efficiency and durability. This article discusses the application of nanocomposite materials in search of new photocatalytic materials for solar hydrogen production from water. It has been demonstrated that smart combination and modification of known materials and functions could be fruitful approach for the purpose.

• Textile Coloration and Finishing
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• v.35 no.2
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• pp.98-106
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• 2023

The recent surge in night walkers and pedestrian traffic accidents has led to an increased interest in retro-reflection-based products, leading to several studies on retro-reflection. Nonetheless, achieving high durability and dispersibility of retro-reflective glass beads in viscous polyurethane coating resin remains challenging. To address this issue, this study conduct to functionalize the surface of glass beads for covalent conjugation to coating resin to enhance their dispersibility and durability in the coating resin. The study evaluated the dispersibility, chemical composition, and retro-reflection properties of the functionalized glass beads and coating resin. The results showed that the functionalized glass beads conjugated to the polyurethane coating resin and exhibited excellent dispersibility, high durability, and maintained retro-reflection efficiency.