• Title, Summary, Keyword: 경화 사이클

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Cure Cycle for Thick Glass/Polyester Composites (두꺼운 유리섬유/폴리에스터 복합재료를 위한 경화 사이클)

  • 김형근;오제훈;이대길
    • Composites Research
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    • v.14 no.2
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    • pp.33-42
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    • 2001
  • The cure kinetic equation fur 52-glass/polyester prepreg composites was established through DSC (differential scanning calorimetry). Using the established kinetic equation, the temperature distribution of the thick composite was calculated considering the change of heat transfer resistance due to resin impregnation of bleeder plies used. In order to reduce the overheat during cure of thick glass fiber composites, the cure cycle was modified by introducing the cooling and reheating steps. Then the thick glass composites were cured both by the conventional cycle without any cooling or reheating step and the modified cure cycle. The mechanical properties of the thick composites cured by the both cycles were tested by the short beam shear test and the Barcol hardness test, and then their results were compared.

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질소첨가 316L 스테인레스 강에서 고온 저주기피로시 발생하는 경화거동

  • 김대환;류우석;김영철;홍준화;최시경
    • Proceedings of the Korean Nuclear Society Conference
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    • pp.463-468
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    • 1996
  • 질소의 함량을 0.04%~0.15% 까지 변화시킨 316L 스테인레스 강으로 공기 중에서 저주기 피로시험을 수행하였다. 전체변형범위 1%, 변형속도 2$\times$$10^3$/sec, 삼각파로 상온 ~$600^{\circ}C$ 온도범위에서 시험을 수행하였다. 상온에서는 사이클이 진행됨에 따라서 연화가 계속해서 발생하지만 온도가 증가하면 초기에 경화가 발생한다. 피로시험 초기에 경화되는 정도와 saturation 응력은 온도가 증가하면 증가한다. 이러한 경화현상은 동적변형시효에 의해서 발생되는 것으로 판명되었다. 질소를 첨가하면 강도는 증가하지만 경화는 감소되었다. 질소에 의한 경화의 감소는 질소가 동적변형시효를 억제하기 때문이다.

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Prevention of Recurrent FSGS with Cyclosporine and Plasmapheresis Prior to Renal Transplantation (신이식 전 예방적 혈장교환술과 사이클로스포린을 이용한 재발성 국소 분절성 사구체 경화증의 효과적인 예방 2례)

  • Yang, Eun-Ae;Park, Hyo-Min;Cho, Min-Hyun;Ko, Cheol-Woo;Kim, Hyung-Kee;Huh, Seung
    • Childhood Kidney Diseases
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    • v.14 no.1
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    • pp.100-104
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    • 2010
  • We report on two children with a high risk of recurrent focal segmental glomerulosclerosis (FSGS) after renal transplantation that could be effectively prevented by prophylactic administration of cyclosporine combined with preemptive plasmapheresis prior to renal transplantation.

Simulation of Ratcheting in Wheel-Rail Contact (차륜-레일 구름접촉에 의한 라체팅 모델링)

  • Goo, Byeong-Choon
    • Journal of the Korean Society for Railway
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    • v.11 no.3
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    • pp.311-316
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    • 2008
  • Ratcheting is a cyclic accumulation of strain under a cyclic loading. It is a kind of mechanisms which generate cracks in rail steels. Though some experimental and numerical study has been performed, modeling of ratcheting is still a challenging problem. In this study, an elastic-plastic constitutive equation with non-linear kinematic hardening equation was applied. Contact stresses in wheel-rail were analyzed. Under the tangential stress of the contact stresses, a cyclic stress-strain relation was obtained by using the model. A constant ratcheting strain per cycle was accumulated.

Cure simulation and Consolidation for a Thick Glass/Epoxy Laminate (유리섬유/에폭시 후판 복합재료의 경화공정 및 압밀해석)

  • O, Je-Hun;Lee, Dae-Gil
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.11
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    • pp.2853-2865
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    • 2000
  • During the curing process of thick glass/epoxy laminates, a substantial amount of temperature lag and overshoot at the center of the laminates is usually experienced due to the large thickness and low thermal conductivity of the glass/epoxy composites. Also, it takes a longer time for full and uniform consolidation. In this work, temperature, degree of cure and consolidation of a 20 mm thick unidirectional glass/epoxy laminate were investigated using an experiment and a 3-dimentional numerical analysis. From the experimental and numerical results, it was found that the experimentally obtained temperature profile agreed well with the numerical one, and the cure cycle recommended by the prepreg manufacturer should be modified to prevent a temperature overshoot and to obtain full consolidation.

Study of Cure Kinetics of Vacuum Bag Only Prepreg Using Differential Scanning Calorimetry (시차주사열량계를 이용한 진공백 성형 프리프레그의 경화 거동 연구)

  • Hyun, Dong Keun;Lee, Byoung Eon;Shin, Do Hoon;Kim, Ji Hoon
    • Composites Research
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    • v.33 no.2
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    • pp.44-49
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    • 2020
  • The cure kinetics of carbon fiber-reinforced prepreg for Vacuum Bag Only(VBO) process was studied by differential scanning calorimetry (DSC). The total heat of reaction (ΔHtotal = 537.1 J/g) was defined by the dynamic scanning test using prepregs and isothermal scanning tests were performed at 130℃~180℃. The test results of isothermal scanning were observed that the heat of reaction was increased as the temperature elevated. The Kratz model was applied to analyze the cure kinetics of resin based on the test results. To verify the simulation model, the degree of cure from panels using different cure cycles were compared with the measurement. The simulation model showed that the error against the experimental value was less than 3.4%.

Investigation of cure cycle for co-cured metal/composite hybrid structures without fabricating thermal residual stress (동시경화 하이브리드 금속/복합재료 구조물의 제조 잔류 열응력 제거를 위한 경화사이클에 관한 연구)

  • Kim Hak Sung;Park Sang Wook;Lee Dai Gil
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.83-87
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    • 2004
  • In this work, the cure cycle of co-cured metal/composite structure was investigated to decrease fabricating thermal residual stresses between the metal and the composite material. DSC (Differential scanning calorimetry) experiment and static lap shear test of co-cured aluminum/composite double lap joint as well as the curvature experiment of co-cured steel/composite strip were performed to investigate the effect of curing cycle on the thermal residual stress of co-cured hybrid structures. From the experiments, it was found that post curing method after abrupt cooling of co-cured aluminum/composite hybrid structure at certain point of degree of cure during curing process could eliminate fabricating the thermal residual stresses.

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Thermal Deformation of Carbon Fiber Reinforced Composite by Cure Shrinkage (탄소섬유강화 복합재료 성형시 화학수축에 의한 변형연구)

  • Choi, Eun-Seong;Kim, Wie-Dae
    • Composites Research
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    • v.31 no.6
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    • pp.404-411
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    • 2018
  • As the autoclave process progresses in a given cure cycle, residual stress in the composite product is induced by cure shrinkage of the resin. As a result, It generates the thermal deformation such as spring-in and warpage, and the inaccuracy of the final product increases. It is important to predict thermal deformation in aerospace parts which require precise fabrication. The research has been done on predicting and grasping curing process of composite material. In this study, the cure mechanism of composite materials according to the process is predicted through finite element analysis, and the effect of cure shrinkage on thermal deformation generated by the process is analyzed.