• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.941-942
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• 2010

• Journal of Power System Engineering
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• v.10 no.2
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• pp.117-123
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• 2006

Woven fabrics composites are used as primary structural components in many applications because of their superior properties that offer high specific strength and stiffness. However, the complexity of the fabric structure makes understanding of their failure behavior very difficult. Also, laminate woven fabrics CFRP have unique failure mechanisms such as fiber bridging, fiber/matrix crack and so on. In particular, the delamination phenomenon of the composite materials is one of the most frequent failure mechanisms. So, we estimated interlaminar fracture and damage in composites using as ENF specimen by a 3 point bending test. And AE characteristics were examined for crack propagation on plain woven CFRP. We obtained the following conclusions from the results of the evaluation of the 3 point bending fracture test and AE characteristic estimation. AE counts of maximum crack length were obtained as $85.97{\times}10^4\;and\;93{\times}10^3\;for\;a_0/L=0.3$ and 0.6, respectively. Also the maximum amplitudes were over 80dB at both $a_0/L=0.3\;and\;0.6$. $G_{IIc}$ at that's $a_0/L$ ratio were obtained with $1.07kJ/m^2\;and\;3.79kJ/m^2$.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.10
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• pp.69-76
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• 2010

This study examined how the fracture toughness is affected according to the variation of the initial crack length and the fiber arranged angle using FEA method and experimental method. Therefore, the energy release rates were calculated and compared by J-integral method and VCCT(Virtual Crack Closure Technique). The results of fracture toughness test verified these results. At this time, the locus method was used in order to determine the energy release rate. When the results of FEA were compared with those of experiment, all of those decreased with the increase of angle between load and the fiber arranged direction. The decrease was due to reducing maximum load and stiffness, and the reason of reduction has been judged that the inplane shear stress.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.12
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• pp.113-118
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• 2010

For a present study, woven type carbon fibers were surface-modified by oxygen plasma to improve adhesive strength between carbon fibers and epoxy. The change of hydrophilic properties by the plasma modification was investigated through the contact angle measurement and the calculation of surface energy of carbon fiber due to the oxygen plasma modification. FESEM and XPS analyses were performed to study the chemical and physical changes on the surface of carbon fibers due to the oxygen plasma modification. Pin-on-disk wear tests were conducted under dry condition using unmodified and plasma-modified carbon/epoxy composites to investigate the effect of plasma modification on the wear behavior of woven type carbon/epoxy composites. The results showed that the friction coefficient and the wear rate of plasma-modified carbon/epoxy composites were lower than those of unmodified carbon/epoxy composites, respectively. XPS analysis showed that new functional group of a carbonyl type was created on the carbon fibers by the $O_2$ plasma treatment, which enhanced adhesive strength between carbon fibers and epoxy, leading to improve wear properties

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.8
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• pp.881-887
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• 2012

CFRP composite materials have been widely used in various fields of engineering because of their excellent properties. They show high specific stiffness and specific strength compared with metallic materiasl. Woven CFRP composite materials are fabricated from carbon fibers with two orientation angles ($0^{\circ}/90^{\circ}$), which influences the mechanical properties. Therefore, woven CFRP composite materials show different types of fracture behavior according to the load direction. Therefore, the fracture behavior of these materials needs to be evaluated according to the load direction when designing structures using these materials. In this study, we evaluate the fracture strength of plain-woven CFRP composite materials according to the load direction. We performed tests for six different angles (load direction: $0^{\circ}/90^{\circ}$, $30^{\circ}/-60^{\circ}$, $+45^{\circ}/-45^{\circ}$) and estimated the fracture strength for an arbitrary fiber angle by using the modified Tan's theory and harmonic function.

• Composites Research
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• v.35 no.4
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• pp.269-276
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• 2022

In this paper, a composite stiffened panel was fabricated using a three-dimensional weaving method that can reduce the risk of delamination, and mechanical properties such as buckling load and natural frequency were investigated. The preform of the stringer and skin of the stiffened panel were fabricated in one piece using T800 grade carbon fiber and then, resin (EP2400) was injected into the preform. The compression test and natural frequency measurement were performed for the stiffened panel, and the results were compared with the finite element analyses. In order to compare the performance of 3D weaving structures, the stiffened panels with the same configuration were fabricated using UD and 2D plain weave (fabric) prepregs. Compared to the tested buckling load of the 3D woven panel, the buckling loads of the stiffened panels of UD prepreg and 2D plain weave exhibited +20% and -3% differences, respectively. From this study, it was confirmed that the buckling load of the stiffened panel manufactured by 3D weaving method was lower than that of the UD prepreg panel, but showed a slightly higher value than that of the 2D plain weave panel.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.585-586
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• 2008

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.374-375
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• 2003

최근 나노섬유기술의 중요성이 증가함에 따라 나노섬유를 제조할 수 있는 여러 방법들 중에 상용화의 가능성, 적용 고분자의 다양성, 제조 공정의 단순성, 다양한 제품기술 응용성을 고려할 때 전기방사는 가장 기대되는 방법으로 현재, 다양한 분야의 연구들이 활발히 진행되고 있다[1,3]. 본 연구는 전기 방사 방법을 이용하여 다공성의 Poly($\varepsilon$-caprolactone) 필라멘트를 제조하고, 제조한 필라멘트를 수직기를 이용하여 평직 직물을 제조하여 그 응용 가능성을 확인하는 것이다[2]. (중략)

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.59-62
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• 2000

In this study, the distribution of the effective modulus was investigated statistically Plain weave structures were modeled with random stacking phase shift angles and the effective modulus was calculated by the unit cell analysis. The analysis results indicated that the effect of random phase shift angles was significant on the modulus distribution. As the number of layers increased, the coefficient of variation decreased and higher degree of homogeneity was attained.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1343-1344
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• 2010