• Journal of Aerospace System Engineering
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• v.5 no.1
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• pp.17-23
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• 2011

Since the time, cost and lack of regulatory information and guidance, one of the largest regulatory obstacles for an airframe manufacturer of polymer based advanced composite materials in certified aircraft applications, is to generate design allowables that will satisfy Airworthiness Regulations. In the past two decades, the design allowables used in military aircraft had been generated and applied in Korea, however the qualification of composite materials used in certifying airframe structure was not accomplished for design and demonstration of compliance to applicable airworthiness regulation. It is the intend of this paper that provide the basis of composite material qualification for small aircraft certification to the airworthiness regulation.

• Journal of the Korean Electrochemical Society
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• v.2 no.2
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• pp.88-92
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• 1999

The apparent density. self-separation of the electrode composite from current collector in the electrolyte solution and specific resistance of electronic conduction of the electrode composite were examined by the variation of content of conductive material such as graphitic and black carbons in $LiCoO_2$ composite electrode for lithium ion battery. Increasing the content of conductive material, the apparent density of Lico02 composite electrode was decreased and that of $LiCoO_2$ in composite electrode was only rapidly decreased compared to that of composite. $LiCoO_2$ composite electrodes containing more than 4.1 weight percent of super s black as a conductive material were seU-separated by the immersion into 1 mol/I $LiPF_6$ in propylene carbonate and diethyl carbonate (1:1 volume ratio). Specific resistances related to the electronic conduction of composite electrode were decreased by the increasing the content i)f conductive material. Specific resistance of the composite electrode including $2\~3\%w/w$ of super s black as conductive material was similar to that of $12\%w/w$ of Lonza KS6. In the range of this study, super s black as conductive material is better than Lonza KS6 on battery capacity because of apparent density of $LiCoO_2$ in electrode composite including super s black is higher than that of Lonza KS6.

• Tribology and Lubricants
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• v.22 no.1
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• pp.1-7
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• 2006

The sliding friction and wear properties of mineral fiber reinforced composite(MF) and glass fiber reinforced composites(GF) are investigated to clarify their field of use and the role of each fiber in friction material. Friction and wear test reveals that GF composite has better wear resistance even though with low friction coefficient, comparing with MF composite. Glass fiber strengthen effectively the matrix and may absorb friction energy to convert it into the fracture energy of them, as well as its lubricative role. However, mineral fiber in MF composite is too small to strengthen the matrix. Then MF composite are easily plowed and worn out by asperity on counter material. Friction coefficient of MF composite is higher friction coefficient than that of GF composite and varied widely with test.

• Journal of Auto-vehicle Safety Association
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• v.13 no.3
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• pp.32-40
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• 2021

Composite material is very attractive because it has excellent mechanical property and is possible to lightweight due to the low density. However, composite material is less used compared to other systems in the chassis system because it is very hard to solve NVH problem when composite material is applied to vehicle. Especially, reducing squeal noise of composite brake system is essential to apply it to vehicle successfully. In this paper, we present a new solution to reduce squeal noise of composite brake system. To achieve this goal, we analyze main causes of noise using RCA (Root Cause Analysis), CA (Contradiction Analysis) and sequentially get IFR (Ideal Final Result) to solve the problem. Next, we define the function of composite brake system and derive control factors and noise factors. A variety of tests for factors like chamfer, slot, damping shim, underlayer of brake pad are done. In addition, we analyze level of contribution for control factors theoretically. Finally, we get the effective solution for reducing squeal noise.

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3227-3232
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• 2013

A novel Cu-Co-O composite nanocatalyst was designed and prepared for the ozonation of phenol. A synergistic effect of copper and cobalt was observed over the Cu-Co-O composite nanocatalyst, which showed higher activity than either copper or cobalt oxide alone. In addition, the Cu-Co-O composite revealed good activity in a wide initial pH range (4.11-8.05) of water. The fine dispersion of cobalt on the surface of copper oxide boosted the interaction between catalyst and ozone, and the surface Lewis acid sites on the Cu-Co-O composite were determined as the active sites. The Raman spectroscopy also proved that the Cu-Co-O composite was quite sensitive to the ozone. The trivalent cobalt in the Cu-Co-O composite was proposed as the valid state.

• Korean Journal of Materials Research
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• v.24 no.5
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• pp.243-248
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• 2014

Silicon-carbon composite was prepared by the magnesiothermic reduction of mesoporous silica and subsequent impregnation with a carbon precursor. This was applied for use as an anode material for high-performance lithium-ion batteries. Well-ordered mesoporous silica(SBA-15) was employed as a starting material for the mesoporous silicon, and sucrose was used as a carbon source. It was found that complete removal of by-products ($Mg_2Si$ and $Mg_2SiO_4$) formed by side reactions of silica and magnesium during the magnesiothermic reduction, was a crucial factor for successful formation of mesoporous silicon. Successful formation of the silicon-carbon composite was well confirmed by appropriate characterization tools (e.g., $N_2$ adsorption-desorption, small-angle X-ray scattering, X-ray diffraction, and thermogravimetric analyses). A lithium-ion battery was fabricated using the prepared silicon-carbon composite as the anode, and lithium foil as the counter-electrode. Electrochemical analysis revealed that the silicon-carbon composite showed better cycling stability than graphite, when used as the anode in the lithium-ion battery. This improvement could be due to the fact that carbon efficiently suppressed the change in volume of the silicon material caused by the charge-discharge cycle. This indicates that silicon-carbon composite, prepared via the magnesiothermic reduction and impregnation methods, could be an efficient anode material for lithium ion batteries.

• 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.

• Composites Research
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• v.24 no.3
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• pp.12-16
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• 2011

High strain rate tensile tests were performed to measure the strain rate sensitivity of fiber reinforced composite material. The composite material was developed for the light weight design of an automotive FEM(front end module) carrier. Standard specimens for quasi-static tests of fiber reinforced composites can be found in ASTM D3039. However, in case of high strain rate tests, it was hard to find standard specimen shapes. In this study, three kinds of tensile specimens designed based on ASTM D638 were investigated to determined the adequate gauge width of tensile specimen for fiber reinforced composite. A drop tower type of high speed tensile apparatus was developed for strain rates of about 15/s and 100/s. Gauge width of 6mm, 8mm and 10mm were investigated. Test results showed the specimen of 8mm width was adequate for the high strain rate tensile tests of fiber reinforced composite. It was found the strength of the composite material increased as the strain rate increased.

• Textile Coloration and Finishing
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• v.33 no.3
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• pp.153-160
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• 2021

In this study, composite materials were prepared by varying the content of glass fiber and bamboo fiber in PP/glass fiber/bamboo fiber. Experiments were conducted to confirm the mechanical properties(tensile, impact and burst strength) and volatile organic compound content of the bamboo fiber composite prepared under these conditions. An improvement in the main properties was observed at a fiber content of 30wt%. When the fiber fraction was increased above 30wt%, the mechanical properties tended to decrease due to the agglomeration of fibers at higher load fractions. In addition, the content of volatile organic compounds increased as the content of bamboo fibers increased, which is thought to be due to the volatile organic compounds generated during the manufacturing process of the composite material being present in the composite material without escaping from the pores of the bamboo fibers and volatilizing at a certain temperature. As a result of confirming the physical properties of the composite, it is considered that the optimal mixing condition is 30wt% of bamboo fiber for the composite produced by varying the amount of bamboo fiber composite. In the future, it is thought that follow-up experiments to confirm and improve the pre-treatment conditions for reducing the content of volatile organic compounds in the manufactured composite material are possible.

• Composites Research
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• v.36 no.5
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• pp.361-368
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• 2023

Composite materials used in aircraft must be certified using approved materials to ensure the the airworthiness of the aircraft. Certification is carried out by verifying the physical properties and processes of the materials, and producing material and process specifications. The composite material certification system in ROK(Republic of Korea) has been established through the MOLIT(Ministry of Land, Infrastructure and Transport) pilot certification project for aircraft composite materials. Currently, the KIAST(Korea Institute of Aviation Safety Technology) operates and manages the certification and shared data system. This study identifies realm for improvement in the established certification system for aircraft composite materials based on empirical evidence and aims to propose measures for the certification and industrial promotion of domestically produced aircraft composite materials.