• Structural Engineering and Mechanics
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• 제59권2호
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• pp.313-326
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• 2016

In this study the three-dimensional nonlinear finite element method was used to analyze the stresses distribution in the adhesive layer used to joint two Aluminum 2024-T3 adherends. We consider in this study the effect of different parameters witch directly affect the values of different stresses. The experimental design method is used to investigate the effects of geometrical parameters of the single lap joint in order to achieve an optimization of the assembly with simple lap joint. As a result, it can be said that both the geometrical modifications of the adhesive and adherends edge have presented a significant effect at the overlap edge thereby causing a decrease in peel and shear stresses. In addition, an analytical model is also given to predict in a simple but effective way the joint strength and its dependence on the geometrical parameters. This approach can help the designers to improve the quality and the durability of the structural adhesive joints.

• Transactions on Electrical and Electronic Materials
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• 제7권1호
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• pp.16-20
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• 2006

In this paper, we investigated the effects of short-term oxygen plasma treatment of semiconducting silicone layer to improve interfacial performances in joints prepared with a insulating silicone materials. Surface characterizations were assessed using contact angle measurement and x-ray photoelectron spectroscopy (XPS), and then adhesion level and electrical performance were evaluated through T-peel tests and electrical breakdown voltage tests of treated semi-conductive and insulating joints. Plasma exposure mainly increased the polar component of surface energy from $0.21\;dyne/cm^2$ to $47\;dyne/cm^2$ with increasing plasma treatment time and then leveled off. Based on XPS analysis, the surface modification can be mainly ascribed to the creation of chemically active functional groups such as C-O, C=O and COH on semi-conductive silicone surface. This oxidized rubber layer is inorganic silica-like structure of Si bound with three to four oxygen atoms ($SiO_x,\;x=3{\sim}4$). The oxygen plasma treatment produces an increase in joint strength that is maximum for 10 min treatment. However, due to brittle property of this oxidized layer, the highly oxidized layer from too much extended treatment could be act as a weak point, decreasing the adhesion strength. In addition, electrical breakdown level of joints with adequate plasma treatment was increased by about $10\;\%$ with model samples of joints prepared with a semi-conducting/ insulating silicone polymer after applied to interface.

• Advances in aircraft and spacecraft science
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• 제11권1호
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• pp.83-103
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• 2024

Adhesive bonding is currently widely used in many industrial fields, particularly in the aeronautics sector. Despite its advantages over mechanical joints such as riveting and welding, adhesive bonding is mostly used for secondary structures due to its low peel strength; especially if it is simultaneously exposed to temperature and humidity; and often presence of bonding defects. In fact, during joint preparation, several types of defects can be introduced into the adhesive layer such as air bubbles, cavities, or cracks, which induce stress concentrations potentially leading to premature failure. Indeed, the presence of defects in the adhesive joint has a significant effect on adhesive stresses, which emphasizes the need for a good surface treatment. The research in this field is aimed at minimizing the stresses in the adhesive joint at its free edges by geometric modifications of the ovelapping part and/or by changing the nature of the substrates. In this study, the finite element method is used to describe the mechanical behavior of bonded joints. Thus, a three-dimensional model is made to analyze the effect of defects in the adhesive joint at areas of high stress concentrations. The analysis consists of estimating the different stresses in an adhesive joint between two 2024-T3 aluminum plates. Two types of single lap joints(SLJ) were analyzed: a standard SLJ and another modified by removing 0.2 mm of material from the thickness of one plate along the overlap length, taking into account several factors such as the applied load, shape, size and position of the defect. The obtained results clearly show that the presence of a bonding defect significantly affects stresses in the adhesive joint, which become important if the joint is subjected to a higher applied load. On the other hand, the geometric modification made to the plate considerably reduces the various stresses in the adhesive joint even in the presence of a bonding defect.

• 한국전기전자재료학회논문지
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• 제19권9호
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• pp.868-872
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• 2006

In this work, the effects of the corona treatment on surface properties of semiconducting silicone rubber were investigated in terms of contact angles, ATR-FTIR(Attenuated total reflection fourier transform infrared spectroscopy) and XPS(X-ray photoelectron spectroscopy). And the adhesive characteristics were studied by measuring the T-peel strengths. Based on chemical analysis, the surface modification can be mainly ascribed to the creation of chemically active functional groups such as C-O, C=O and C-OH on semiconducting silicone surface. This oxidized rubber layer is inorganic silica-like structure of Si bound with three to four oxygen atoms ($SiOx,\;x=3{\sim}4$. The Corona treatment produces an increase in joint strength that is maximum for 10 min treatment. However, due to brittle property of this oxidized layer, the highly oxidized layer from too much extended treatment could be act as a weak point, decreasing the adhesion strength.

• 마이크로전자및패키징학회지
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• 제15권2호
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• pp.7-15
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• 2008

본 논문에서는 ACF를 이용한 CCM용 COF 어셈블리의 실장 기술을 연구하고 COF 어셈블리의 신뢰성 분석을 수행하였다. 열팽창계수, 모듈러스, 유리전이온도 등 경화 후 ACF의 열-기계적 물성들을 분석하였으며, ACF의 경화거동 결과를 바탕으로 COF 접합공정 온도 및 시간을 최적화하였으며, 도전입자의 변형 관찰 및 전기적 접촉 저항 측정을 통해 본딩 압력에 대한 최적화를 수행하였다. 또한 ACF 물질 특성이 COF어셈블리의 신뢰성에 미치는 영향을 알아보기 위해 열-싸이클 시험, 고온 유지 시험, 고온고습 시험을 수행하였다. 신뢰성 시험 수행 후 ACF를 이용한 COF 어셈블리의 신뢰성에 가장문제가 되고 있는 점은 열-싸이클 신뢰성 시험에서 나타난 ACF joint의 접촉 저항 증가 문제였고, 이는 ACF 자체의 열-기계적 물성과 밀접한 관계가 있음을 확인하였다.

• Composites Research
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• 제13권4호
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• pp.42-53
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• 2000

차세대 항공기소재로 관심을 가지고 있는 Al 7075/CFRP 적층 복합재인 CARALL(CARbon ALuminum Laminates)하이브리드 복합소재 제조를 위한 중요조건중의 하나인 Al 표면처리조건과 경화방법에 대해 조사하였다. 항공기용 Al 전처리 중 대표적인 것으로 증기탈지, 크롬산 양극산화 피막처리, 황산-중크롬산 나트륨 에칭처리 및 인산 양극산화 피막처리공정이 있다. 본 실험에서는 상기 전처리 공정을 모두 항공 규격에 준해서 실시하여 Lap shear 및 Bell peel strength를 비교함으로써 효과적인 접착강도를 나타내는 표면처리 공정을 찾아내고, 시편의 자연표면상태를 그대로 관찰할 수 있는 AFM(Atomic Force Microscope)장비를 이용하여 각 전처리 시편의 표면형상을 측정함으로써 표면형상과 접착강도와의 상관관계를 고찰 하였다. 그리고 Al 표면처리와 별도로 Al과 접착제 및 탄소섬유 프리프레그를 동시에 경화시키는 방법과 탄소섬유 프리프레그를 미리 경화시킨후 다시 Al과 탄소섬유 라미네이트를 접착필름을 이용하여 재 접착시키는 이차 경화법을 적용하여 상호 접착강도 및 물성을 비교하였다. 또한 이차경화법에서의 오토클레이브 압력 변화와 DMA(Dynamic Mechanical Analysis) 장비를 이용한 접착필름의 유리전이온도($T_g$) 측정을 통해 효과적인 공정압력 및 접착내구성 유지에 필요한 최소 경화시간을 파악하였다. 상기 결과로부터 정밀 치수관리가 필요하며 고접착강도, 내구성 항공기 부품을 제작하기 위한 알루미늄 표면처리 공정과 복합재 경화공정 조건을 제시하고자 하였다.