• Composites Research
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• v.31 no.6
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• pp.299-303
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• 2018

In order to improve the interfacial bonding force and reaction polymerization degree of the carbon fiber reinforced nylon 6 composite material, the surface of the existing epoxy-sizing carbon fiber was desized to remove the epoxy and treated with urethane, nylon and phenoxy sizing agent, was observed. The interfacial bond strength of the resized carbon fiber was confirmed by IFSS (Interfacial Shear Strength) and the fracture surface was observed by scanning electron microscope. The results showed that the interfacial bonding strength of the carbon fiber treated with nylon and phenoxy sizing agents was higher than that of urethane - based sizing. It has been found that the urethane - type resizing carbon fiber has lower interfacial bonding strength than the conventional epoxy - sizing carbon fiber. This result shows that the interfacial bonding between carbon fiber and nylon 6 is improved by removing low activity and smoothness of existing carbon fiber.

• Composites Research
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• v.26 no.5
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• pp.315-321
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• 2013

In this work, pitch-carbonized glass fibers were prepared for reinforcement of composites. The influence of acid functionalization of the fibers on the morphological, mechanical, and thermal properties of fiber-reinforced epoxy matrix composites was investigated. The acid functionalization of the fibers led to 10 and 150% increases in the mechanical and thermal properties, respectively, as compared to carbon fiber-reinforced composites. This can be attributed to the superior orientation of fiber structures and good interfacial interactions between fillers and epoxy matrix, resulting in enhanced degree of dispersion and formation of thermally conductive paths in the functionalized composites.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.10
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• pp.113-120
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• 1995

여러가지 두꺼운 복합재료 구조물은 3차원 압축 부하 상태에 노출되는 경우가 발생한다. 이런 경우에 있어 서의 복합재료 압축 강도는 압축 평균 응력을 이용하면 예측이 가능할지도 모른다. 이번 연구 에서는 압축 평균 응력을 이용하여 탄소섬유 강화 복합재료들의 압축 강도를 예측하는 모델을 개발 하고자 한다. 이 모델은 압축강도에 영향을 주는 요소, 초기 misalignment를 고려하였고, 탄소섬유와 수지사이에 접합강도가 임계값을 초과할때 복합재료의 파괴가 일어난다고 가정한다. 또 여라가지 문헌들을 통하여 유압이 접합강도에 미치는 점들을 보여준다. 본 모델을 이용한 예측값들은 가해지는 유압에 따라 증가되며, 실험값들과 비교 분석될 것이다.

• Proceedings of the Korean Magnestics Society Conference
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• 1995.05a
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• pp.36-37
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• 1995

• Composites Research
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• v.32 no.6
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• pp.349-354
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• 2019

The Aluminum conductor composite core consists of fast-curing thermosetting epoxy used as reinforcements and carbon fiber and glass fiber used as matrix. In this study, we have investigated fast curing epoxy cured products used for composite core(Aluminum Conductor Composite Core, ACCC). Tetrafunctional epoxy(PA 806) was used as a multifunctional epoxy, along with two kinds of curing agents, MNAn(5-Methyl-5-norbornene-2,3-dicarboxylic anhydride) and HHPA(Hexahydrophthalic Anhydride), to make an epoxy cured product and their properties were evaluated. Optimum conditions are confirmed by varying the content of curing accelerator in the selected epoxy and curing agent.

• Composites Research
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• v.15 no.3
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• pp.39-44
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• 2002

Interfacial properties and microfailure modes or electrodeposition(ED) treated carbon fiber reinforced polyetherimide(PEI) toughened epoxy composites were investigated using microdroplet test. ED was performed to improve the interfacial shear strength(IFSS). As PEI content increased, IFSS increased due to enhanced toughness and plastic deformation of PEI. In the untreated cafe, IFSS Increased with adding PEI content, and IFSS of pure PEI matrix showed the highest. On the other hand, thor ED-treated case IFSS increased with PEI content with rather low improvement rate. In the untreated case, neat epoxy resin appeared brittle microfailure mode, whereas pure PEI matrix exhibited more likely ductile microfailure mode. In the ED-treated case, neat epoxy exhibited more ductile fracture compared to the untreated case. Interfacial properties of epoxy-PEI composite can be affected efficiently by both the control of matrix toughness and ED treatment.

• Composites Research
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• v.29 no.3
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• pp.111-116
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• 2016

The tilting pad journal bearing for the turbo compressor application has a role to support high speed and heavy loading rotor. White metal has been widely used for the bearing material but the conventional bearing is immediately suspended and induces serious serious damage to the rotor under the unexpected oil cut situation or the insufficient oil film formation. The carbon fiber reinforced composite having high specific stiffness, specific strength and excellent tribological characteristics can solve these seizure problems. In this work, the study on the durability of high thermal resistance carbon fiber/epoxy composite tilting pad journal bearing under oil cut situation was conducted. The material properties of the composite materials including tensile, compressive and interlaminar properties were measured at room and high temperature of oil cut situation. To investigate the possibility of failure of composite tilting pad journal bearing under oil cut situation, the stress distribution of the composite bearing was analyzed via finite element analysis and the Tsai-Wu Failure index was calculated. To verify the failure analysis results, the oil cut tests for the composite tilting pad journal bearing were conducted using industrial test bench.

• Composites Research
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• v.34 no.3
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• pp.148-154
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• 2021

Carbon/epoxy composite bipolar plate (BP) is a BP that is likely to replace existing graphite bipolar plate of vanadium redox flow cell (VRFB) due to its high mechanical properties and productivity. Multi-functional carbon/epoxy composite BP requires graphite coating or additional surface treatment to reduce interfacial contact resistance (ICR). However, the expanded graphite coating has the disadvantage of having low durability under VRFB operating conditions, and the surface treatments incur additional costs. In this work, an excessive resin absorption method is developed, which uniformly removes the resin rich area on the surface of the BP to expose carbon fibers by applying polyester fabric. This method not only reduces ICR by exposing carbon fibers to BP surfaces, but also forms a unique ditch pattern that can effectively hold carbon felt electrodes in place. The acidic environmental durability, mechanical properties, and gas permeability of the developed carbon/epoxy composite BP are experimentally verified.

• Composites Research
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• v.30 no.6
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• pp.365-370
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• 2017

Mechanical properties of carbon fiber reinforced thermoplastic composites (CFRTPs) are affected by various factors. One of the them are poor compatibility of the epoxy sizing layer on the carbon fiber surface with thermoplastic matrix, which causes the inferior interfacial strength between fibers and matrix. In addition, the high molten-viscosity of thermoplastics attributes to the poor impregnation state. Consequently, many voids in the composite materials were generated, which leads to poor mechanical properties of the thermoplastic composites. In this study, the epoxy sizing on the carbon fiber surface was removed and the polyamide 6,6 solution was coated on the de-sized carbon fiber surface to improve the impregnation state and mechanical properties. Interlaminar shear strength (ILSS) of CFRPTs was estimated by implementing short beam shear tests. In addition, flexural strength was measured and the impregnation state of the composites was evaluated by calculating void content.

• Composites Research
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• v.30 no.3
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• pp.215-222
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• 2017

The effect of a multi walled carbon nanotubes (MWNCT) on the adhesive properties and thermal properties of epoxy were studied by double lap-shear tests. Epoxy/MWCNT resins were prepared from a different amount of the MWCNT incorporated into the epoxy resins (araldite 2011). Steel plates and carbon fiber reinforced plastics (CFRP) were chosen as materials. Mechanical tests were performed by a universal testing machine (UTM). The analysis of thermal properties were conducted by a thermogravimetric analyzer (TGA) and a differential scanning calorimetry (DSC). The fracture surface morphology was examined using a scanning electron microscopy (SEM) and optical microscope. Compared to neat epoxy, it was found that the mechanical properties of epoxy/MWCNT resins are increased.