• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.394-395
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• 2003

絲(bundle)와 구성섬유(fiber)간의 인장물성 관계를 규명하기 위한 연구는 오래전부터 계속되어 왔다[1-4]. 그러나, 과거의 연구들은 주로 면사와 같은 단섬유(short staple)를 중심으로 이루어졌으며, 합성섬유와 같은 장섬유(continuous filament)의 경우 불균제가 작다는 이유로 스테이플에 비해 소홀시 되어왔다. 조사에 의하면 합성섬유도 생산국 및 제조사에 따른 絲의 인장물성은 큰 차이를 나타내므로[5], 필라멘트의 인장물성에 대한 연구의 중요성도 간과할 수 없다. (중략)

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.81-85
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• 2006

Through-the-thickness properties of thick-walled cylindrical composites are required to determine structural performances because interlaminar tensile stress is primarily responsible for structural failure of the composites during their curing process. It is necessary for evaluating the tensile properties to find individual test methods to find appropriate methods because there are no recognised international standards(test methods and test specifications) available for generating reliable tensile properties in the direction. This paper has performed an experimental Study to measure that properties of carbon fabric/phenolic composites are produced by domestic company. Several test methods using an aluminum specimen were compared and evaluated. The best method, found out, was adopted to measure transverse through-the-thickness properties of composite materials. The results show that strain trends on four faces of composite specimen are the same.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.3
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• pp.48-52
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• 2006

Through-the-thickness properties of thick-walled cylindrical composites are required to determine structural performances because interlaminar tensile stress is primarily responsible for structural failure of the composites during their curing process. It is necessary for evaluating the tensile properties to find individual test methods to find appropriate methods because there are no recognised international standards(test methods and test specifications) available for generating reliable tensile properties in the direction. This paper has performed an experimental study to measure that properties of carbon fabric/phenolic composites which are produced by domestic company. Several test methods using an aluminum specimen were compared and evaluated. The best test method to measure transverse through-the-thickness properties of composite materials was developed by the experimental results that strain trends on all faces of composite specimen are the same.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.73-78
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• 2010

Estimation of tensile properties measurement uncertainty of material was carried out. Sources of uncertainty affecting the measurement of tensile properties were classified and analyzed. The models for uncertainty evaluation of measurands to be determined from tensile test, such as elastic modulus, yield strength and tensile strength, were suggested and derived from the mathematical relations, corresponding to the respective measurands, and the measuring quantities by calculating each sensitivity coefficient of the quantities. Based on these models, the uncertainty of the tensile properties was evaluated from the experimental data of SUS316LN determined according to ISO 6892.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.7
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• pp.769-776
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• 2012

The damage analysis method in this paper needs a material property and failure criteria. The material properties and the failure criteria could be easily obtained from the results of notched bar tensile tests carried out on other materials studied previously. However, for the cast stainless steel (CF8M) material in this paper, because of the variance in the results from notched bar tensile tests under the same conditions, the material property and the failure criteria could be obtained differently, depending on the analyzer. Therefore, a proper procedure that can confirm the material property and failure criteria are needed. In this work, the averaged material property was obtained from the notched bar with a 16-mm notch radius, and three failure criteria for CF8M material by finite element analysis were obtained. Applying the material property and the failure criteria, FE damage analysis for the J-R fracture toughness test was conducted. For validation, the simulated results were compared with the experimental results.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.10
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• pp.14-19
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• 2004

• Composites Research
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• v.17 no.6
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• pp.1-7
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• 2004

The studies of particulate reinforced composites have been conducted for many years. The nanocomposites to be studied vigorously in recent years are one of them. We fabricated and studied multi-walled carbon nanotube(MWNT)/epoxy composites which may be useful as matrix for continuous fiber-reinforced composites. We investigated tensile properties of MWNT/epoxy composites as a function of MWNT concentration, which were prepared by the fabrication method established in this study. Tensile stiffness and strength increased 19% at 0.5 wt% and 12% at 0.2 wt%, respectively. We observed the reaggregation phenomenon of MWNTS during curing, which should be controlled to obtain higher tensile properties.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.39.1-39.1
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• 2010

겨울철 혹한지방에서의 차량운행 또는 여름철 혹서지방에서의 장시간 차량 운행시 차체를 구성하고 있는 강판에는 약 $-50^{\circ}C{\sim}150^{\circ}C$의 온도환경에 처하게 된다. 따라서 이러한 저온 고온 환경하에서 차체 충돌상품성 예측 및 충돌안전 설계를 위해 온도에 따른 차체 강판의 기계적 물성평가가 요구된다. 이를 위해 본 연구에서는 자동차용 충돌부재에 주로 쓰이는 HS440MPa, HS590MPa급 냉연 고장력 강판에 대해 $-60^{\circ}C{\sim}200^{\circ}C$의 온도범위로 저온 고온 인장시험을 수행 하였다. 각각의 인장시험 결과로부터 온도 별 항복강도, 인장강도, 연신율, 가공경화지수 등 기계적 물성 변화를 평가하였다. 저온 고온 인장시험은 ZWICK Z250 만능재료시험기를 사용하였고 KS5호 규격의 인장시편을 사용하였으며, 시편에 충분한 온도를 가하기 위하여 목표온도 도달 후 20분간 유지한 뒤 인장시험을 수행하였다. 인장시험결과 HS440MPa, HS590MPa급 두 강종 모두 온도가 낮아질수록 강도 및 연신율 등이 증가하였고, 온도가 증가할수록 강도 및 연신율 등 기계적 물성이 저하 되었다. 즉, 우리가 주로 평가해왔던 상온($25^{\circ}C$)에 비해 저온 고온 환경하에서는 강판의 기계적 물성 변화가 큰 것을 알 수 있다. 따라서 혹한 또는 혹서 지방 등 온도차이가 큰 운행환경하에서의 차체 강도 및 충돌안전성 확보를 위해 온도에 따른 강판의 정확한 물성평가가 필요하고 차체 설계시 온도에 따른 강도변화를 충분히 고려하여야 한다.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.2
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• pp.147-153
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• 2013

Recently the primary water stress corrosion cracking(PWSCC) has occurred in the dissimilar metal weld region between pressurizer nozzle and safe-end in nuclear power plants(NPPs). As material of the pressurizer nozzle, SA508 Gr. 3 low alloy steel was used. F316L stainless steel and Alloy 82/182 were used as safe-end and weld metal, respectively. Although mechanical properties are needed for evaluation of the structural integrity against flaw in the material, material specification and standard don't supply those properties. Therefore, the present study conducted tensile and fracture toughness tests on SA508 Gr.3 and F316L stainless steel at ambient temperature and operating temperature of NPPs and reported the tested results.

• Composites Research
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• v.20 no.4
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• pp.1-8
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• 2007

In this study, carbon fiber reinforced polymeric (CFRP) composites with different resin composition were manufactured and resin formulation in composite materials were presented through tensile tests for cryogenic use. Thermo-mechanical cyclic loading (up to 6 cycles) was applied to CFRP unidirectional laminate specimens from room temperature to $-150^{\circ}C$. Tensile tests were then performed at $-150^{\circ}C$ using an environmental test chamber. In addition, matrix-dominant properties such as the transverse and in-plane shear characteristics of each composite model were measured at $-150^{\circ}C$ to examine the effects of resin formulation on their interfacial properties. The tensile tests showed that the composite models with large amounts of bisphenol-A epoxy and CTBN modified rubber in their resin composition had good mechanical performance at cryogenic temperature (CT).