• Macromolecular Research
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• 제13권3호
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• pp.223-228
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• 2005

In the present work, a low-density polyethylene (LDPE) composite, filled with Zn-ion coated structural silica encapsulated with the diglycidyl ether of bisphenol-A (DGEBA), was synthesized using the conventional melt-blending technique in a sigma internal mixer. The catalytic activity of the Zn-ions (originating from the structural silica) towards the oxirane group (diglycidyl ether of bisphenol-A (DGEBA): encapsulating agent) was assessed by infrared spectroscopy. Two composites, each with a filler content of $2.5 wt\%$ were developed. The first one was obtained by melt blending the Zn-ion coated structural silica with LDPE in a co-rotating sigma internal mixer. The second one was obtained by melt blending the same LDPE, but with DGEBA encapsulated Zn-ion coated structural silica. Epoxy resin encapsulation of the Zn-ion coated structural silica resulted in its having good interfacial adhesion and a homogeneous dispersion in the polymer matrix. Furthermore, the encapsulation of epoxy resin over the Zn-ion coated structural silica showed improvements in both the mechanical and thermal properties, viz. a $33\%$ increase in the elastic modulus and a rise in the onset degradation temperature from 355 to $371^{\circ}C$, in comparison to the Zn-ion coated structural silica.

• 한국재료학회지
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• 제11권12호
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• pp.1009-1013
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• 2001

The effects of coupling agent on the interface characteristics between epoxy resin and natural zeolite were studied by SEM, optical microscope and universal testing machine (UTM). Epoxy resin as a matrix was diglycidyl ether of bisphenol A (DGEBA)/4,4'-methylene dianiline (MDA)/malononitrile (MN) system and natural zeolite as an inorganic fillet was produced in Korea. With the increment of zeolite content, tensile strength decreased and it was due to the different elastic moduli of two materials. When external stress was loaded on the composites, the stress concentrated on the weakly bonded interface and crack grew easily. To improve the interface characteristics, the surface of the natural zeolite was treated with the silane coupling agent and it was found that the tensile strength was increased. The morphology of the interface showed that the bonding characteristics were modified by coupling agent.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.438-441
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• 2004

In this study, we investigated compressive characteristics of seawater-absorbed carbon-epoxy composite under hydrostatic pressure environment. The hydrostatic pressures applied were 0.1 MPa, 100 MPa, 200 MPa, and 270 MPa. The results showed that the compressive elastic modulus increased about 10 ％ as the hydrostatic pressure increased from 0.1 MPa to 200 MPa. The modulus increased 2.3 ％ more as the pressure increased to 270 MPa. Fracture strength and fracture strain increased with pressure in a linear fashion. Fracture strength increased 28 ％ and fracture strain increased 8.5 ％ as the hydrostatic pressure increased from 0.1 MPa to 270 MPa.

• 한국전기전자재료학회논문지
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• 제30권10호
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• pp.641-645
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• 2017

In this study, an epoxy insulation barrier for high voltage GIS was developed using epoxy and a filler with a Young's modulus of 11 GPa. The material was investigated using a simulation of the principal stress, displacement, and safety factors while optimizing the profile shape. The simulation showed that thelarger Young's modulus of the $Al_2O_3$ filler compared to the $SiO_2$ in the epoxy insulation can contribute to an increase in resistance to mechanical fracturing for theoptimized profile barrier in high voltage GIS. In addition, the safety factor was improved by 10%. It can be concluded that the mechanical fracturing properties of the insulation barrier can be enhanced by increasing the content of the elastic filler, $Al_2O_3$, for high voltage GIS applications.

• 유변학
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• 제3권1호
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• pp.22-29
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• 1991

In an effort to predict the long term durability of carbon fiber/epoxy composites in a space environ-ment interlaminar shear strength (ILSS) of the composites was measured as a function of 0.5 MeV electron radiation dosage. For the ILSS measurements a notch method (ASTM D3846) was used with and without side-supports. the supports were used to prevent peeling or bending during the test. The ILSS of both T300/ 5209 longitudinal composite system increases monotonically with radiation when the test is corried out without the support the ILSS of the composites increases initially but then decreases with further radiation. It is also observed that the ILSS of the unsupported case is much lower than that of the supported case. Measurement of epoxy modulus shows that the elastic modulus increases monotonically with radiation. But the breaking strength of the epoxy decreases with radiation. Electron Spectroscopy for Chemcal Analysis shows that the oxygen contents at both the pure epoxy surface and the composite fracture surface increase with radiation dose resulting in the increase of polarity at the interfacial region. This may be a supporting evidence for the increase in the ILSS of the composites.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.406-409
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• 2004

In this study, we investigated compressive characteristics of seawater-absorbed carbon-epoxy composite under hydrostatic pressure environment. The hydrostatic pressures applied were 0.1 MPa, 100 MPa, 200 MPa, and 270 MPa. The results showed that the compressive elastic modulus increased about 10 % as the hydrostatic pressure increased from 0.1 MPa to 200 MPa. The modulus increased 2.3 % more as the pressure increased to 270 MPa. Fracture strength and fracture strain increased with pressure in a linear fashion. Fracture strength increased 28 % and fracture strain increased 8.5 % as the hydrostatic pressure increased from 0.1 MPa to 270 MPa.

• Composites Research
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• 제12권1호
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• pp.59-67
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• 1999

보강섬유의 굴곡을 가지는 일방향성 graphite/epoxy 복합재료의 비선형거동에 대하여 이론 및 실험을 통하여 고찰하였다. 해석모델에서 공액에너지밀도와 순차적 해석방법을 이용하여 보강섬유의 굴곡에 의한 재료적 비선형 특성 및 기하학적 비선형 특성을 모두 고려하였으며, 이를 이용하여 보강섬유의 굴곡정도에 따른 복합재료의 기계적 특성값의 변화 및 인장/압축 거동을 일정한 보강섬유의 굴곡을 가지는 모델, 재료의 중심에서 바깥쪽으로 갈수록 보강섬유의 굴곡이 점차 줄어드는 모델 그리고 재료의 일부분에만 보강섬유의 굴곡이 존재하는 모델에 대하여 예측하였다. 그리고 여러 굴곡 정도에 대한 일정한 보강섬유의 굴곡을 가지는 두꺼운 복합재료를 제작하고 인장/압축 실험을 수행하여 그 결과와 예측 결과를 비교하였다. 실험 결과는 예측 결과와 잘 일치하였으며, 보강섬유의 굴곡이 복합재료의 기계적 특성에 큰 영향을 미침을 알 수 있었다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.1-4
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• 2001

A new non-destructive fatigue prediction model of the composite laminates is developed. The natural frequencies of fatigue-damaged laminates under extensional loading are related to the fatigue lift of the laminates by establishing the equivalent flexural stiffness reduction as a function of the elastic properties of sublaminates. The flexural stiffness is derived by relating the $90^{\circ}$-ply elastic modulus reduction, and using the laminate plate theory to the degraded elastic modulus and the intact elastic modulus of other laminate. The natural frequency reduction model, in which the dominant fatigue mode can be identified from the sensitivity scale factors of sublaminate elastic properties, provides natural frequency vs. fatigue cycle curves for the composite laminates. Vibration tests were also conducted on $[\textrm{90}_{2}\textrm{0}_{2}]_s$ carbon/epoxy laminates to verify the natural frequency reduction model. Correlations between the predictions of the model and experimental results are good.

• 대한기계학회논문집A
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• 제20권10호
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• pp.3211-3223
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• 1996

In this paper, the propagation of elastic wave generated by loading impact to plates made of isotropic of anisotropic material was studied. And the influence of boundary conditions (free or clamped edge) upon the reflection of elastic wave was anlyzed. Also, double exposure holographic interferometer using ruby pulse laser was formed in order to investigate transient waves. Before the elasitc wave was reflected from the edges, the elastic wave of isotropic plate such as aluminum plate showed circular interferometric fringe pattern, whereas that of anisotropic plate such as epoxy composite laminates showed elliptical one. And the transverse displacement curves obtained from experiment and theory for both plates agreed well. Also, the waves reflected from the boundary edges showed much differences according to the boundary condition of edges.

• Composites Research
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• 제28권5호
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• pp.260-264
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• 2015

본 논문에서는 CNT강화 에폭시 복합재의 열기계적 거동을 예측하고 그 경향을 분석하기 위해 분자동역학 시뮬레이션을 이용하여 해석을 수행하였다. 에폭시 내부 CNT의 체적비율을 0~25%까지 총 6개의 모형을 구성하였다. 열적 거동을 보기 위해 300~600 K까지 일정하게 온도를 상승시켰으며, 온도와 비체적 관계를 이용하여 유리전이 온도와 열팽창 계수를 산출하였다. 또한 일정 변형도 하중을 통해 탄성 계수를 산출하여 기계적 거동을 예측하였다. 추가적으로 CNT의 표면처리에 따른 기계적 거동을 분석하였다. 질소 도핑 및 COOH, OH 그룹을 처리한 3개의 모형을 구성하였으며, 각 모형의 탄성 계수 및 경계면 거동에 대한 해석을 수행하였다. 이를 통해 에폭시 내부 CNT의 응집은 열기계적 거동에 교란을 가지고 올 수 있으며, 표면처리는 복합재의 기계적 물성뿐만 아니라 경계면 특성까지도 향상시킬 수 있음을 확인하였다.