• 대한기계학회논문집A
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• 제20권3호
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• pp.806-815
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• 1996

The interlaminar fracture behavior of woven laminates under static and cyclic loadings has been studied using DCB(double cantilever beam) specimens. The effects of surface treatment and stiching on the fracture behavior of composite laminates are investigated experimentally. Fracture toughness has been improved by surface treatment because the surface treatment can change the fracture mechanism of laminates. SCB(stitched cantilever beam) model has been proposed to quantify the effect of through-thickness resinforcement(stiching) in improving the delamination crack growth resistance. Distributed loads which are transfered to through-thickness fibers can be calculated by the SCB model. And fracture energy increase due to the distributed load can be predicted by a power function of the distributed load. A new parameter agreed well proposed predict fatigue crack growth rate. The predictions using this parameter agreed well with the experimental data.

• Composites Research
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• 제14권1호
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• pp.8-14
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• 2001

복합재 적층판의 자유단 층간분리의 모드별 변형률 에너지 해방률을 구하는 간이 계산법을 제안하였다. 층간응력은 층간에서의 평형식으로부터 층간의멘트와 층간전단력으로 평가하였다. 적층판 자유단 층간분리의 변형은 일반화된 준3차원 고전적층이론에 의하여 계산하였다. 이 간이 계산법은 변형균 에너지 해방률의 세성분을 구하는 간편한 식으로 나타내었다 복합재 적층판이 일축인장을 받는 경우에 대하여 적층판 중앙면에 대칭과 비대칭인 층간분리가 발생한 경우에 대하여 해석을 행하였다. 해석결과는 가상분리진전법에 의한 유한요소해석결과와 잘 일치하였다.

• Structural Engineering and Mechanics
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• 제76권2호
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• pp.175-191
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• 2020

In this study, the effect of Nano silica (SiO2) on the buckling strength of the glass fiber reinforced laminates containing the machining process causes holes were investigated. The tests have been applied on two status milled and non-milled. To promote the mechanical behavior of the fiber-reinforced glass epoxy-based composites, Nano sio2 was added to the matrix to improve and gradation. Nano sio2 is chosen because of flexibility and high mechanical features; the effect of Nanoparticles on surface serenity has been studied. Thus the effect of Nanoparticles on crack growth and machining process and delamination caused by machining has been studied. We can also imply that many machining factors are essential: feed rate, thrust force, and spindle speed. Also, feed rate and spindle speed were studied in constant values, that the thrust forces were studied as the main factor caused residual stress. Moreover, entrance forces were measured by local calibrated load cells on machining devices. The results showed that the buckling load of milled laminates had been increased by about 50% with adding 2 wt% of silica in comparison with the neat damaged laminates while adding more contents caused adverse effects. Also, with a comparison of two milling tools, the cylindrical radius-end tool had less destructive effects on specimens.

• 한국가구학회지
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• 제15권2호
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• pp.19-27
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• 2004

As glulam is a woody material, it is necessary to be more careful in a gluing process. It takes 6-7 hours at $40-60^{\circ}C$ to harden PRF resin used in making structural glulam, and about 24 hours at room temperature. In the present process which can not use a press continuously, reducing the hardening time is necessary to increase production. The experiment was done to compare the adhesive properties of PRF resin and MUF resin through bending test, block shear strength test and water soaking test. In comparing the bending strength of prediction MOE is 1.2 times higher that actual MOE. PRF and MUF do not show significant difference in MOE and MOR, and in block shear strength test, such as shear strength and wood failure rate. However, in water soaking and boiling water soaking tests PRF and MUF show the significant difference in delamination rate.

• 수산해양기술연구
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• 제51권3호
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• pp.454-460
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• 2015

The present study is undertaken to evaluate the effect of volume fraction on the results of Charpy impact test for the rubber matrix filled with nano sized silica particles composites. The Charpy impact tests are conducted in the temperature range $0^{\circ}C$ and $-10^{\circ}C$. The range of volume fraction of silica particles tested are between 11% to 25%. The critical energy release rate $G_{IC}$ of the rubber matrix composites filled with nano sized silica particles is affected by silica volume fraction and it is shown that the value of $G_{IC}$ decreases as volume fraction increases. In regions close to the initial crack tip, fracture processes such as matrix deformation, silica particle debonding and delamination, and/or pull out between particles and matrix which is ascertained by SEM photographs of Charpy impact fracture surfaces.

• 수산해양기술연구
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• 제51권4호
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• pp.561-566
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• 2015

In this study, the effect of temperature effect of the rubber matrix filled with nano sized silica particles composites with silica volume fraction of 19-25% was investigated by the Charpy impact test. The Charpy impact test was conducted in the temperature range from $-40^{\circ}C$ to $0^{\circ}C$. The critical energy release rate GIC of the rubber matrix composites filled with nano sized silica particles was considerably affected by temperature and it was shown that the maximum value was appeared at higher temperature between temperature tested and it was shown that the value of GIC increases as temperature tested increases. The major fracture mechanisms were matrix deformation, silica particle debonding and delamination, microcrack between particles and matrix, and/or pull out between particles and matrix which is ascertained by SEM photographs of Charpy impact surfaces fracture.

• 한국해양공학회지
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• 제22권6호
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• pp.35-40
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• 2008

The effect of counterpart roughness on abrasive wear characteristics of side plate materials of FRP ship, which were composed of glass fiber and unsaturated polyester resin composites, were investigated at ambient temperature by pin-an-disc friction test. The friction coefficient, wear rate and cumulative wear volume of these materials against SiC abrasive paper were determined experimentally. The wear rate of these materials decreased rapidly with sliding distance and then maintained a constant value. It was increased as counterpart roughness was rougher in a wear test. The cumulative wear volume tended to increase nonlinearly with sliding distance and depended on applied load and sliding speed for these composites. It could be verified by SEM photograph of fracture surface that major failure mechanisms were overlapping layers, microcutting, deformation of resin, delamination, and cracking.

• Composites Research
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• 제23권4호
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• pp.21-27
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• 2010

대부분의 구조물 파괴는 피로에 의해서 발생한다. 따라서 지금까지 모드 혼합비가 피로 특성에 어떤 영향을 미치는지에 대한 수많은 연구가 수행되어 오고 있다. 하지만 대부분의 연구가 금속/금속 계면이나 복합재료 층간 분리에 관한 연구이다. 따라서 본 연구에서는 이종재료인 복합재료/금속 계면의 피로 특성에 대한 기초 자료를 얻고자 하였다. 이를 위하여 복합재료와 탄소강을 동시 경화법을 이용하여 접합한 SLB(single leg bending) 시편을 이용하여 피로 실험을 수행하였다. 특히, 피로 특성에 모드 혼합비$(G_{II}/G_T)$가 어떠한 영향을 미치는지에 대해 알아보고자 하였다. 전체적으로 모드 II 하중 성분 이 많을수록 균열진전속도가 빨라진다는 결과를 얻었다.

• 대한조선학회논문집
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• 제44권6호
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• pp.627-634
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• 2007

A bonded plate or a coated part can be debonded by external impact or thermal expansion. To analyse adhesive strength, the blister test is generally adopted. In this paper, a blister test is modelled theoretically and then the stability and bifurcation of the blister are studied under several different cases. The blister is simplified to consist of a pure bending plate attached elastically to the rigid substrate. Expression of the energy release rate is obtained as a form of an explicit function for a circular-type blister or tunnel-type blister grown by controlling the internal pressure or internal volume. Stability and bifurcation are also studied in the frame of the quasi-static evolution. The study shows that the circular- type blister propagates with the first mode of bifurcation and that the tunnel-type blister propagates with a regular wave. It is proved that the waves have the same form on two side lines of the tunnel and that the wave length can be obtained. When the internal pressure is controlled, the blister is unstable, but when the internal volume is controlled, it is stable.

• Elastomers and Composites
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• 제48권2호
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• pp.167-171
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• 2013

자동차용 선도장 베이스코트 도료에서 사용되는 알루미늄의 입자 크기와 배향에 따른 내후성을 연구하였다. UV를 촉진하여 조사할 수 있는 QUV$^{(R)}$ (Q-LAB) 장비를 이용하여 UV 투과율의 차이에 의한 소재의 손상 정도를 관찰하였다. Conflake 형태의 입자 크기가 서로 다른 3종의 알루미늄 paste를 이용하여 자동차용 선도장 조건으로 베이스코트를 도장하고 투명 클리어를 도장하여 필름과 시편을 제조하였다. 작성된 필름을 UV 투과 장비로 측정한 결과 입자 크기가 작고 수평 배향인 EKART사의 #790을 사용 시 낮은 UV 투과율을 나타내었다. 실제 내후성 시편의 단면 조사에서도 #790, #770, #750 순으로 높은 광택 유지율을 나타내었다.