• Journal of Korea Ship Safrty Technology Authority
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• no.7 s.25
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• pp.64-76
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• 2008

This paper describes the failure mechanism and Charpy impact test of Fiber glass Reinforced Plastic composites which it was actually used for side plate of vessel. There are two examinations. The examination I, the specimens which it given temperature range $-25^{\circ}C$-$50^{\circ}C$ and with different initial notch length did impact test and then it compared impact energy(Uc) and impact fracture toughness(GIC). The examination II, the specimens which it putted into fresh water and sea water for scheduled hours did impact test and it compared impact energy(Uc) and impact fracture toughness(GIC). From examination I, it showed that impact energy(Uc) and impact fracture toughness(GIC) were peak at ambient temperature and decrease as temperature reduced. Fracture toughness(GIC) showed increase as initial notch length reduced. From examination II, impact energy(Uc) and impact fracture toughness(GIC) tended to increase which specimens putted in fresh water compared with sea water and maximum tolerance rate tend to decrease as permeation hours will be long.

• The Korean Journal of Rheology
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• v.8 no.2
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• pp.129-138
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• 1996

접착강도는 접착제의 점탄성을 반영한 온도·속도 의존성을 나타낸다는 것이 잘 알 려져있다. 특히 유리전이온도(Tg)에서의 역학적 완화기구가 접착층의 변형을 수반하는 접착 층의 변형을 수반하는 접착강도에 크게 영향을 미치고 있다. 또한 접착계의 모드I의 변형에 너지 해방율(GIC)를 측정할때에도 접착제의 변형과 파괴가 발생하기 접착제의 점탄성이 그 값에 어떠한 영향을 미치는 지에 흥미가 깊다. 본 연구에서는 2종류의 에폭시 수지를 블랜 드한 접착제를 이용하여 일정한 측정조건에서 인장 접착강도와 GIC의 상관관계에 대하여서 도 토론하였다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.4
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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.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.05a
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• pp.314-319
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• 2004

Many of researches regarding mechanical properties of composite materials are associated with humid environment and temperature. Especially the temperature is a very important factor influencing the design of thermoplastic composites. However, the effect of temperature on impact behavior of reinforced composites have not yet been fully explored. An approach which predicts critical fracture toughness GIC was performed by the impact test in this work The main goal of this work is to study effects of temperature in the impact test with glass fiber/polypropylene(GF/pp) composites. The critical fracture energy and failure mechanisms of GF/PP composites are investigated in the temperature range of $60^{\circ}C\;to\;-50^{\circ}C$ by impact test. The critical fracture energy shows a maximum at ambient temperature and it tends to decrease as temperature goes up or goes down. Major failure mechanisms can be classified such as fiber matrix debonding, fiber pull-out and/or delamination and matrix deformation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.3
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• pp.611-623
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• 1998

The delamination fracture of multidirectional carbon-fiber/epoxy laminates under the Mode I condition has been studied using the modified beam analysis for a fracture mechanics approach. It was found that the variation of fracture energy $G_IC$ with increasing length of the propagating crack exhibited a minimum for the pure interlaminar fracture and a maximum for the intraply fracture,i.e. a rising "R-curve", which was strongly affected by the degree of fiber bridging and crack-tip splitting arising in the global delamination. The maximum $G_IC$ value was significantly dependent on such types of delamination as no crack jumping, crack jumping into the adjacent ply and edge-delamination. It was shown also that the value of "effective flexural modulus" estimated from the modified beam analysis increased much with the development of fiber bridging behind the crack tip.ehind the crack tip.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.4
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• pp.161-169
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• 2000

Recycled aggregates were generated when concrete structures were dismembered. However, in concrete structures, because of durability, strength and toughness, recycled aggregates don't use generally. This study was done to use recycled aggregate in concrete structures. Problems of durability, strength, and toughness were caused troubles, when recycled aggregates were used, were solved as steel fibers and additives were added. Of course, steel fiber length, steel fiber contents, additive substitution, and recycled aggregate substitution were variables of this study. After flexural specimens($15{\times}15{\times}70cm$) with notch(45mm) were fabricated, basic strength tests were done and toughness was estimated using fracture mechanics parameters. The results suggest that JIC is a promising fracture criterion for all of these, while KIC(or GIC) almost certainly are not.

• Composites Research
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• v.12 no.5
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• pp.40-53
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• 1999

The interlaminar facture behavior of multidirectional carbon-fiber/epoxy composite laminates under low and high rates of test, up to rate of about 11.4m/s has been investigated using the double cantilever beam specimens. The mode I loasing with rates above 1.0m/s had considerable dynamic effects on the load-time curves and thus revealed higher values of the average crack velocity than thet expected from a simple proportional relationship with the test rate. The modified beam analysis utilizing only the opening displacement and crack length exhibited an effective means for evaluating the dynamic fracture energy $G_{IC}$. Flexural modulus increased gradually with an increase of the test rate, which was utilized in the evaluation of $G_{IC}$. Values of $G_{IC}$ at the crack initiation and arrest were scarcely changed with increasing test rate up to 1.0m/s. However the maximum $G_{IC}$ was much enlarged at 11.4m/s due to the large amount of fiber bridging the crack tip. The larger the initial crack length, the smaller the maximum $G_{IC}$ at high rate.