• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.115-118
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• 2003

This research aims to measure mechanical tensile properties of CFRP composites for cryogenic tank material. Through the cryogenic chamber, tensile tests are peformed under cryogenic temperature for graphite/epoxy fabric specimen aged at $-150^{\circ}C$ for 30hrs with load and graphite/epoxy unidirectional specimen 3-cycled from RT to $-100^{\circ}C$ with load. For graphite/epoxy fabric specimen, tensile modulus showed to increase after aging at cryogenic temperature(CT) while to decrease after aging at room temperature(RT) and tensile strength is more decreased after CT-aged than at RT-aged. For graphite/epoxy unidirectional specimen, tensile modulus was almost not changed after 3-cycling but strength showed the trend of decrease as increase the number of cycling.

• 소성∙가공
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• 제13권5호
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• pp.409-414
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• 2004

TRIP steel has got attention in automobile industry because of its high strength and high formability. However, the information on deformation behavior of TRIP steel, including bending and springback, is not enough until now. In this research, the V-die bending experiment and analysis have been done to obtain the information of springback of TRIP steel. And a new numerical method, where elastic modulus is varied with the change of the strain, was suggested. Tensile test for TRIP steel was done to get tensile properties as well as strain dependency of elastic modulus of the material. Strain-dependency of elastic modulus was used the numerical analysis of V-die bending and unbending process to predict springback amount. The results were compared with experiment, showing reasonable agreement. Through the analysis of V-die bending as well as draw bending of TRIP steel, the proposed scheme with variable elastic modulus was proven to well predict the deformation behavior of TRIP steel during bending and springback.

• 한국염색가공학회지
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• 제17권1호
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• pp.30-37
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• 2005

The tensile properties, acetic acid solubility and degree of swelling in distilled water of cellulose/chitosan and sericin/chitosan film blended by mixing chitosan acetic acid solution with cellulose solution or sericin solution were investigated and the effect of crosslinking agent on solubility and degree of swelling were also considered. From the experimental results, the model of intermolecular bond is proposed. Tensile modulus of 100% cellulose film is high but the tensile strength and elongation are low. The elongation of 100% chitosan film is high but tensile modulus and strength is low. But it is possible to make film having same or higher tensile strength and modulus compared to that of 100% cellulose film by mixing cellulose and chitosan or by mixing sericin and chitosan. Chitosan is solved in 5vol % acetic acid solution but cellulose and sericin are not solved. Degree of swelling of chitosan in distilled water is higher than that of cellulose and sericin. Lower than 40wt% chitosan content, the solubility of cellulose/chitosan film in 5vol % acetic acid solution shows lower expected value but higher in case of sericin/chitosan film.

• 한국응용과학기술학회지
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• 제26권2호
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• pp.171-178
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• 2009

A comparative analysis of the hindered amine light stabilizers (HALS) and UV abosrber (UVA) and their respective photostabilizing effect on wood plastic composites (WPCs) are reported in this study. The influence of accelerated weathering on the mechanical properties of the composites and the microscopic morphology of a degraded layer on the cross section and the surface were studied. UV absorbers were more efficient at preventing composite lightening than was UV stabilizer. The amount of whitening decreased with the increase of photostabilizers. With the addition of a UV absorber (Tinuvin360), the tensile modulus and strength of the composites increased slightly. However, the addition of a light stabilizer (Tinuvin770) and a UV absorber decreased the tensile modulus and strength of the composites. After 250 and 500 hr exposure, tensile modulus and strength of the un stabilized and stabilized composites decreased. The tensile strength of UV absorber (Chimassorb81)-stabilized composites was significantly greater than that of control and light stabilizer (Tinuvin770)- and UV absorber (Tinuvin360)-stabilized composites. UV absorber-stabilized samples showed less whitening and photodegradation than control and light stabilizer-stabilized samples.

• 한국응용과학기술학회지
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• 제24권4호
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• pp.416-426
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• 2007

Polypropylene (PP) composites with wood flour/wax/coupling agent were manufactured by melt compounding and injection molding. The influence of wood flour(WF), wax, and coupling agent on the mechanical and thermal properties of the composites was investigated. The addition of wood flour to neat PP has the higher tensile modulus and strength compared with neat PP. The presence of wax also improved the tensile modulus. At the same loading of PP and WF, the addition of coupling agent highly decreased the tensile modulus, and increased the tensile strength. From thermogravimetric analysis (TGA), the addition of wax improved the thermal stability of the composites in the later stages of degradation. The presence of MAPP and wood flour in turn decreased thermal stabilities of composites. From differential scanning calorimetry analysis (DSC), neither the loading of wax. nor the presence of MAPP has shown significant effect on the thermal transition of composites.

• 대한기계학회논문집A
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• 제24권7호
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• pp.1697-1702
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• 2000

This study has been performed to investigate the effects of glass fiber characteristics on the mechanical properties of thermoplastic composite. The surface of glass fiber was coated with the silan e to enhance the bonding strength between fiber and matrix. A micro-droplet pull-off test was performed to investigate the influence of the silane concentration on the bonding strength. The maximum bonding strength was observed around 10.8% silane concentration. In order to examine the influence of the fiber length and fiber content on the properties of the composite, the composite materials involving tile fiber lengths of 5mm, 10mm, 15mm 20mm, and 25mm were tested. The composites used contain 20%, 30%, and 40% by weight of glass fibers. Tension and flexural tests were performed to investigate their mechanical properties of the composites. The tensile strength and tensile modulus of the composite increase with increasing the glass fiber content. The tensile modulus increases slightly with increasing the fiber length. The maximum tensile strength is observed around the fiber length of 15-20mm. The flexural modulus and strength also increase slightly with increasing the fiber length.

• 한국도로학회논문집
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• 제9권4호
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• pp.205-213
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• 2007

본 연구에서는 포장용 콘크리트의 강도실험을 통해 강도간의 상관관계식을 도출하는 것을 목적으로 하였다. 강도로서 재령별 압축강도, 휨강도, 할렬인장강도와 탄성계수를 측정하였다. 배합변수는 조골재(화강암, 석회암, 사암), 세골재(자연사, 세척사, 부순모래) 및 단위시멘트량(315-375kg)을 변수로 하였다. 전체적으로 골재나 단위시멘트량보다는 재령에 의해 전형적인 강도곡선을 따라 뚜렷하게 변화함을 보여준다. 이러한 강도결과를 바탕으로 휨강도와 압축강도, 할렬인장강도와 압축강도, 탄성계수와 압축강도, 할렬인장강도와 휨강도의 상관관계를 분석한 결과 휨강도와 압축강도, 탄성계수와 압축강도는 기존의 관례대로 제곱근(n=0.5)의 상관관계식이 잘 맞음을 알 수 있었다. 할렬인장강도와 휨강도는 선형의 상관관계식으로 표현하였고, 할렬인장강도와 압축강도는 n=0.87의 지수승을 사용한 경우가 가장 적합한 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제65권3호
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• pp.343-348
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• 2018

This paper reports mechanical behavior of recycled fine aggregate concretes after high temperatures. It is found that compressive strength of recycled fine aggregate concretes decline significantly as the temperature rises. The elastic modulus of recycled fine aggregate concretes decreases with the increase in temperature, and the decrease is much quicker than the decrease in compressive strength. The split tensile strength of recycled fine aggregate concrete decrease as the temperature rises. Through the regression analysis, the relationship of the mechanical behavior with temperature are proposed, including the compressive behavior, elastic modulus and split tensile strength, which are fitting the test data.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제28회 춘계학술대회논문집
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• pp.189-192
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• 2007

고무제품의 경우 구조성능평가를 위해 단축인장, 순수전단, 이축인장 및 압축시험을 수행한다. 일반적으로 단축인장시험값을 기초물성으로 사용하며 용도에 따라 다른 시험을 수행한다. 검증을 위해 단축인장시험/해석 결과를 비교하여 타당성을 확인했다. 본 연구에서는 전단강성이 주요인자인 제품의 성능평가를 위해 단축인장시험에서 획득한 물성을 적용한 QLS 해석모델의 결과를 비교, 검증하였다.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 1988년도 학술발표초록집
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• pp.35-37
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• 1988

This paper shows the possibility of the application of the orientation density function of fibers to the mechanics of fibrous assembly. As an example, the orientation density function of a single yarn was theoretically derived in consideration of the idealized helical yarn. And the theoretical derivation of the tensile modulus of the fibrous assembly was performed in view of the fiber orientation. Application of this orientation density function to the obtained tensile modulus and to the contraction factor of the yarn was also performed so that the theoretical equations of the tensile modulus and the contraction factor of the yarn were obtained. Close agreement was shown between the theoretical and the existing equations. Consequently it was confirmed that the application of the orientation density function to the mechanics of the fibrous assembly is sufficiently possible.