• Composites Research
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• 제25권5호
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• pp.136-140
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• 2012

본 논문에서는 복합재료 IM rod가 적용된 골절부의 세포 분화과정을 모사하기 위해 유한요소해석을 실시하였다. 세포의 골화과정을 해석하기 위해 편향 변형률을 이용한 메카노 규제 이론을 사용하였으며, 반복 계산을 위해 Python 코드를 이용하여 서브루틴을 구현하였다. 치료에 가장 적절한 복합재료 IM rod의 강성을 찾기 위해 직물 탄소섬유/에폭시 복합재료 (WSN3k)의 적층각도를 바꾸어 해석을 실시하였다. 골절부에 가해지는 기계적 자극에 따른 치료효율을 비교하기 위해 두 가지 초기 하중 조건을 적용하였다. 그 결과 치료효율은 강성의 차이보다 하중에 의해 큰 영향을 받았으며, 초기 하중이 몸무게의 10%이고, 적층순서가 $[{\pm}45]_{nT}$일 때 치료효율이 가장 높았다.

• 한국공작기계학회논문집
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• 제10권1호
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• pp.88-93
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• 2001

Carbon fiber epoxy composite are widely used in airframe structures, space vehicles, sports equipment, and high speed reciprocating parts for industrial machinery. In this paper, the groove processing characteristics of carbon fiber epoxy com-posite was experimentally investigated in order to study the endmill operation of fiber reinforce epoxy composites. Followings are main finding from the experimental results. First, the cutting and bending force in groove processing of the carbon fiber epoxy composite increased as the spindle speed deceased. They also deceased as the table feed increased. Second, the good cutting status obtained at the entrance of groove while delamination occurred at the exit of groove, Third, the regular high speed steel endmill was not efficient, thus the new endmill such as coated carbide rooter endmill or dia-mode endmill should be used for the effective endmll operation of carbon filber epoxy composites.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.88-91
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• 2002

The two dimensional size effect of specimen gauge section (length x width) was investigated on the compressive behavior of a T300/924 [45/-45/0/90]3s, carbon fiber-epoxy laminate. A modified ICSTM compression test fixture was used together with an anti-buckling device to test 3mm thick specimens with a 30$\times$30, 50$\times$50, 70$\times$70, and 90mm$\times$90mm gauge length by width section. In all cases failure was sudden and occurred mainly within the gauge length. Post failure examination suggests that $0^{\circ}$ fiber microbuckling is the critical damage mechanism that causes final failure. This is the matrix dominated failure mode and its triggering depends very much on initial fiber waviness. It is suggested that manufacturing process and quality may play a significant role in determining the compressive strength. When the anti-buckling device was used on specimens, it was showed that the compressive strength with the device was slightly greater than that without the device due to surface friction between the specimen and the device by pretoque in bolts of the device. In the analysis result on influence of the anti-buckling device using the finite element method, it was found that the compressive strength with the anti-buckling device by loaded bolts was about 7% higher than actual compressive strength. Additionally, compressive tests on specimen with an open hole were performed. The local stress concentration arising from the hole dominates the strength of the laminate rather than the stresses in the bulk of the material. It is observed that the remote failure stress decreases with increasing hole size and specimen width but is generally well above the value one might predict from the elastic stress concentration factor. This suggests that the material is not ideally brittle and some stress relief occurs around the hole. X-ray radiography reveals that damage in the form of fiber microbuckling and delamination initiates at the edge of the hole at approximately 80% of the failure load and extends stably under increasing load before becoming unstable at a critical length of 2-3mm (depends on specimen geometry). This damage growth and failure are analysed by a linear cohesive zone model. Using the independently measured laminate parameters of unnotched compressive strength and in-plane fracture toughness the model predicts successfully the notched strength as a function of hole size and width.

• 한국수소및신에너지학회논문집
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• 제25권2호
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• pp.131-138
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• 2014

Highly conductive bipolar plate for polymer electrolyte membrane fuel cell (PEMFC) was prepared using phenol novolac-type epoxy/graphite powder (GP)/carbon fiber filament (CFF) composite, and a rubber-modified epoxy resin was introduced in order to give elasticity to the bipolar plate graphite fiber (GF) was incorporated in order to improve electrical conductivity. To find out the cure condition of the mixture of novolac-type and rubber-modified epoxies, differential scanning calorimetry (DSC) was carried out and their data were introduced to Kissinger equation. And tensile and flexural tests were carried out using universal testing machine (UTM) and the surface morphology of the fractured specimen and the interfacial bonding between epoxy matrix and CFF or GF were observed by a scanning electron microscopy (SEM).

• 한국해양공학회지
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• 제29권2호
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• pp.186-190
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• 2015

$TiO_2$ nanoparticles can be used to improve the performance of carbon fiber-reinforced epoxy resin composites. In this study, the effect of the size of $TiO_2$ nanoparticles on the mechanical properties of carbon fiber-reinforced epoxy resin composites was investigated. The size of the $TiO_2$ nanoparticles was easily controlled using heat treatment. The size of the $TiO_2$ nanoparticles for this study were20nm, 100nm, and 200nm. Three types of carbon fibers with different diameters were also used in this study. The carbon fiber-reinforced epoxy resin composites with 20-nm $TiO_2$ powder showed the highest tensile strength compared to the other types of CFRP, regardless of the fiber maker or fiber diameter. The size of the $TiO_2$ powder and the diameter of the carbon fiber strongly affected the interfacial properties of all kinds of CFRP in this study.

• 대한기계학회논문집A
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• 제30권7호
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• pp.857-864
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• 2006

Various compressive specimens were fabricated using autoclave do-gassing moulding to find out the compressive characteristics of the carbon/epoxy plain weave fabric composites with respect to the bias and shear angles. The stacking angles of the bias specimens are $[0]_{10T,}\;[3]_{10T,}\;[6]_{10T,}\;[9]_{10T,}\;[12]_{10T,}\;[15]_{10T,}\;[30]_{10T,}\;[45]_{10T}$ and those of the sheared specimens are $[{\pm}37]_{10T,}\;[{\pm}32]_{10T,}\;[{\pm}28]_{10T,}\;[{\pm}22]_{10T,}$ respectively. In order to verify the effect of micro-tow structures on compressive strength and modulus of the composites, compressive test specimens of uni-directional carbon/epoxy composites with the same materials and the same stacking conditions were fabricated. The modulus and strength of both types of composite specimens were compared with the prediction results based on the CLPT and a proposed strength formula. The tow deformation and fracture modes were investigated by microscopic observation.

• 한국해양공학회지
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• 제14권3호
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• pp.90-99
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• 2000

This study has been investigated about the influence of moisture environment properties in the unidirectional and cross laminated carbon fiber/epoxy and glass fiber/epoxy composites. As a results, it was found that the weight gain of water increased with the immersion time and the mechanical properties were decreased with the weight gain of water. And it was also shown that the mechanical properties of carbon fiber/epoxy laminates were better than those of glass fiber/epoxy laminates. And a gap of the mechanical properties between the two kinds of laminates was increasing with the immersion time in distilled water of 80$^{\circ}C $. Mechanical properties which decreased by moisture absorption in the CF and GF reinforced laminates were recovered up to some extent by drying in oven at 80$^{\circ}C $ for 10 days.

• 비파괴검사학회지
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• 제23권5호
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• pp.418-428
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• 2003

섬유파단은 복합재료의 기계적물성을 규명하는 가장 중요한 현상 중 하나이며, 섬유파단 위치는 기지재료의 물성과 섬유표면 처리에 따라 광학현미경에 의한 방법뿐만 아니라 음향방출법을 이용하여 확인 및 상호비교 할 수 있다. 두 개의 음향방출 센서를 단일섬유강화 에폭시 복합재료 시편 표면에 부착 시켜 연속적인 섬유파단 신호를 변형률과 측정 시간에 따라 감지하였으며, 계면전단강도는 단일섬유강화 복합재료 시험에서 광학적 방법과 음향방출법을 이용하여 측정하였다. 탄소섬유의 파단 수는 섬유표면을 전기증착으로 처리한 경우가 많았으며, 광학적인 관찰 시에 좀 더 많게 나타났다. 하지만 음향방출법과 광학적 방법에 의한 섬유파단의 위치는 작은 오차범위 내에서 상호 잘 일치하는 결과를 얻을 수 있었다. 음향방출법에 의한 섬유파단 위치표정과 파형분석은 투명, 반투명 및 불투명한 복합재료의 계면물성을 비파괴적으로 측정하기 위한 유용한 방법으로 사료된다.

• Composites Research
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• 제37권1호
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• pp.15-20
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• 2024

수소탱크의 잔류응력은 내구도와 직접적인 관련이 있기 때문에 안전을 위해 이를 줄이는 것이 매우 중요하다. Type II~IV 수소탱크는 섬유에 수지를 함침시켜 라이너에 감는 필라멘트 와인딩 공법으로 제작하게 된다. 필라멘트 와인딩에서 잔류응력은 경화조건, 섬유 인장 등에 영향을 받게 되는데, 본 연구에서는 탄소섬유 필라멘트 와인딩 공정을 이용한 Type III 수소탱크 제작 시 경화조건이 잔류응력에 미치는 영향을 분석하였다. 먼저 에폭시 수지의 경화거동을 시차주사열량계를 이용하여 분석하였다. 이를 통해 경화온도를 140℃로 설정하였다. 같은 경화시간 동안 140℃에 먼저 도달하는 2-stage 경화조건과, 보다 늦게 도달하는 4-stage 경화조건으로 각각 시편을 경화시켰다. 경화 후 복합재 부분의 잔류응력을 ring slitting 법으로 측정하였고, 이 실험값을 수치해석적인 값과 비교하였다. 그 결과, 경화조건 최적화에 따른 유의미한 잔류응력의 차이가 발생함을 확인하였다.

• 접착 및 계면
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• 제23권1호
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• pp.1-7
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• 2022

풍력블레이드가 대형화되면서 유리섬유 복합재료(GFRP)와 탄소섬유 복합재료(CFRP)를 혼용하여 제작하고 있고, 이 때 두 가지 이종재료 간의 접착특성에 대한 연구가 활발히 진행되고 있다. 본 연구에서는 에폭시 접착제 내 탄소나노튜브 함량 및 경화 시 습도의 차이에 따른 접착강도의 변화를 평가하였다. 탄소나노튜브의 함량이 다른 에폭시 접착제를 활용하여 GFRP와 CFRP를 접착하였고, 경화 시 습도에 따른 특성의 변화를 알아보기 위해 접착강도를 평가하였다. 탄소나노튜브 함량에 따른 변화를 알아보기 위해 접착제에 들어가는 탄소나노튜브의 함량을 0, 0.1, 0.3, 0.5, 1 wt%로 나누어 단일 랩 전단 시험을 진행하였고, 습도 조건에 따른 변화를 확인하기 위해 항온항습기로 습도를 20, 50, 80% 조건으로 나누어 접착제를 경화시킨 후 단일 랩 전단 시험을 진행하였다. 실험결과 에폭시 접착제에 탄소나노튜브를 넣음으로써 접착특성이 향상됨을 확인하였지만 함량이 과도하게 많을 때에는 접착력이 줄어드는 것을 확인하였다. 또한 습도가 증가할수록 접착특성이 변하지 않음을 확인할 수 있었다.