• 대한치과보철학회지
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• 제32권3호
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• pp.411-430
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• 1994

The denture may be fractured accidentally by an impact while outside the mouth, or may be cracked or broken while in service in the mouth. The latter is generally a fatigue failure caused by repeated flexure over a period of time. This investigation compared the flexural fatigue resistance, the impact force and the transverse strength of two denture base materials with and without the grid strengthener, the T300, the T800 and the Kevlar fiber to evaluate the fracture resistance. The distribution and behavior of fibers across fracture lines were examined by Hi-Scope Compact Microvision System. Through analyses of the data from this study, the following conclusions were obtained. 1. The flexural fatigue resistance, impact strength and transverse strength of high impact strength resin were higher than those of conventional heat polymerizing resin, but statistically there was no significant difference(p>0.05). 2. All specimens with and without the grid strengthener did not show significant differences in the flexural fatigue, the impact and the transverse strength test(p>0.05). 3. All specimens reinforced with the T300, the T800 and the Kevlar fiber showed significant increase of the fatigue resistance and the impact force(p<0.05). 4. All specimens reinforced with the T800 and the Kevlar fiber showed significant increase of the transverse strength(p<0.05). 5. All specimens reinforced with the T300, the T800 and the Kevlar fiber exhibited greenstick fractures. The fibers tended to remain enveloped in the resin, resisting pull-out.

• Composites Research
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• 제14권2호
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• pp.1-7
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• 2001

본 논문은 항공기 노스콘(nose cone) 제작에 사용되는 Kevlar/Epoxy 프리프레그의 조성과 경화거동을 연구한 것이다. 이 소재의 경화거동을 dielectrometer와 시차주사열분석기를 사용하여 연구하였다. 이 프리프레그는 $120^{\circ}C$ 부근에서 가장 낮은 이온점도를 보였으며, 이 이후 경화반응의 진행과 함께 점도가 $200^{\circ}C$ 까지는 상승하는 경향을 보여 주었다. 이것은 이 프리프레그의 경화반응이 $120^{\circ}C$ 부근에서 개시됨을 의미하며, 이 온도 이후부터 가속화된 분자간 가교화 반응을 통해서 분자량이 현저히 커짐을 의미한다. 본 프리프레그의 dynamic scan에 따른 loss factor 및 tan $\delta$값을 측정/연구하였는데, 매트릭스의 유동성과 매우 밀접한 관계에 있는 loss factor 거동은 이온점도 거동과 매우 유사하였다. 본 프리프레그의 열반응 특성을 시차주사열분석기를 사용해서 연구하였다.

• Restorative Dentistry and Endodontics
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• 제25권3호
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• pp.371-380
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• 2000

The effect of fiber reinforcing materials on the fracture strength of composite resin was evaluated. Each ten composite resin bars reinforced by glassfiber[Fiber-Splint ML$^{(R)}$(Polydentia SA, Switzerland)], polyethylene fiber [Ribbond$^{(R)}$(Ribbond Inc., U.S.A.)] and polyaramid fiber[Kevlar$^{(R)}$(DuPont, U.S.A.)] were loaded under the 3-point compression technique. Another ten pure composite resin bars without reinforcement were used as a control group. Then mean fracture strength and standard deviation were calculated and a ANOVA and Scheffe test were used in statistics. The results were as follows: 1. Kevlar group showed the highest fracture strength as 175.5MPa (p<0.05). Fiber-Splint ML group showed the lowest fracture strength as 112.7MPa. 2. The mean value of fracture strength in Ribbond group was 136.4MPa, and that of unterated control group was 143.6MPa. No difference was found between the two groups. 3. Ribbond and Kevlar reinforcement groups showed a catastrophic failure, where complete separation of pieces occurs to a unseparated fracture pattern. The use of Kevlar reinforcement fibers with composite resin showed significant increase in the average load failure and the presence of the fibers did prevent the catastrophic crack propagation present in the unreinforced samples. The use of Ribbond reinforcement fibers with composite resin showed no significant increase in the average load failure. However, the presence of the fibers did prevent the catastrophic crack propagation. Because high strength of glassfiber are rapidly degraded on exposure to moisture and humidity. The use of Fiber-Splint ML reinforcement fibers with composite resin showed significant decrease in the average load failure and displayed catastrophic fractures.

• 한국초전도ㆍ저온공학회논문지
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• 제20권4호
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• pp.11-15
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• 2018

Torque tubes in High Temperature Superconducting (HTS) motor transfer torque from superconducting field winding rotor to the room temperature shaft. It should have minimum heat conduction property for minimizing the load on cryo-refrigerator. Generally, these torque tubes are made with stainless steel material because of high strength, very low outgassing and low thermal contraction properties at cryogenic temperatures and vacuum conditions. With recent developments in composite materials, these torque tubes could be made of composites such as Kevlar and S-Glass, which have the required properties like high strength and low thermal conductivity at cryogenic temperatures, but with a reduced weight. Development and testing of torque tubes made of these composites for HTS motor are taken up at Bharat Heavy Electricals Limited (BHEL), Hyderabad in collaboration with Central Institute of Plastics and Engineering Technology (CIPET), Chennai and Indian Institute of Technology (IIT), Kharagpur. As these materials are subjected to vacuum, it is important to measure their outgassing rates under vacuum conditions before manufacturing prototype torque tubes. The present study focusses on the outgassing characteristics of Kevlar and S-Glass, using an Outgassing Measurement System (OMS), developed at IIT Kharagpur. The OMS facility works under vacuum environment, in which the test samples are exposed to vacuum conditions over a sufficient period of time. The outgassing measurements for the composite samples were obtained using pressure-rise technique. These studies are useful to quantify the outgassing rate of composite materials under vacuum conditions and to suggest them for manufacturing composite torque tubes used in HTS motors.

• Advanced Composite Materials
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• 제16권2호
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• pp.95-113
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• 2007

Experimental investigations of interlaminar mechanical properties for carbon fiber reinforced plastic (CFRP) laminates were carried out using aramid fiber ($Kevlar^{(R)}$-29 1000d) and carbon fiber (TR40-1K 612d, Mitsubishi Rayon) stitching. Various carbon fiber (CF) stitch densities were used to prepare a number of CF stitched CFRP laminates for double cantilever beam (DCB) tests. An insert tongue-type loading fixture, developed by the Japan Aerospace Exploration Agency (formerly the National Aerospace Laboratory of Japan), was also employed in the DCB test. Interlaminar tension tests were carried out under an out-of-plane directional loading using a single CF stitch thread in the CFRP laminates. The DCB test results clarified that the relationship between the volume fractions of the CF stitch thread ($V_{ft}$) and mode I critical energy release rate ($G_{Ic}$) showed a mostly linear function with a higher gradient than that of the $Kevlar^{(R)}$ stitched CFRP laminates. The CF stitched CFRP tension test results indicated that the consumption energy per unit area ($E_i$) was larger than that of $Kevlar^{(R)}$ stitched CFRP laminates.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 1995년도 춘계학술발표회 프로그램 및 초록
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• pp.18-18
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• 1995

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 1994년도 추계 학술발표회
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• pp.142-142
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• 1994

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 1994년도 춘계학술발표회 프로그램 및 초록
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• pp.82-82
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• 1994

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 1994년도 춘계학술발표회 프로그램 및 초록
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• pp.105-106
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• 1994

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 1994년도 춘계학술발표회 프로그램 및 초록
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• pp.107-107
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• 1994