• Title/Summary/Keyword: Preform

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Study on Out-of-plane Properties and Failure Behavior of Aircraft Wing Unit Structures (항공기 날개 부분 단위구조체의 면 외 방향 물성 및 파손거동에 관한 연구)

  • Yoon, Chang-Mo;Lee, Dong-Woo;Byun, Joon-Hyung;Tran, Thanh Mai Nguyen;Song, Jung-il
    • Composites Research
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    • v.35 no.2
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    • pp.106-114
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    • 2022

  • Carbon fiber-reinforced plastic, well known high specific strength and high specific stiffness, have been widely used in the aircraft industry. Mostly the CFRP structure is fabricated by lamination of carbon fiber or carbon prepreg, which has major disadvantage called delamination. Delamination is usually produced due to absence of the through-thickness direction fiber. In this study, three-dimensional carbon preform woven in three directions is used for fabrication of aircraft wing unit structure, a part of repeated structure in aircraft wing. The unit structure include skin, stringer and rib were prepared by resin transfer molding method. After, the 3D structure was compared with laminate structure through compression test. The results show that 3D structure is not only effective to prevent delamination but improved the mechanical strength. Therefore, the 3d preform structure is expected to be used in various fields requiring delamination prevention, especially in the aircraft industry.

  • https://doi.org/10.7234/composres.2022.35.2.106 인용 PDF KSCI HTML

A Study on Precuring Condition of the 2-step Manufacturing Method for PEMFC Composite Bipolar Plates (PEMFC용 복합소재 분리판을 위한 2단계 제조공법의 예비성형 조건에 대한 연구)

  • Heo, Seong-Il;Oh, Kyung-Seok;Jang, Jun-Ho;Yang, Yoo-Chang;Han, Kyung-Seop
    • Composites Research
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    • v.20 no.2
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    • pp.10-16
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    • 2007

  • The 2-step manufacturing method consisting of preforming and stamping processes was developed to manufacture composite bipolar plates for PEMFCS. The preform was composed of expanded graphite, graphite flake and phenol resin. Procuring conditions were optimized by checking the electrical conductivity, flexural strength and microstructure. Procuring temperature $(100^{\circ}C)$ slightly above the melting point of phenol powders $(90^{\circ}C)$ induced moderate curing, but also prevented excessive curing. Preforms utilizing the tangled structure of expanded graphite were easily fabricated at low pressure of 0.07-0.28MPa. The proper procuring time, 5min, was determined to fabricate the preform stably because insufficient and excessive procuring deteriorated the flexural strength of composite bipolar plates.

  • https://doi.org/10.7234/kscm.2007.20.2.010 인용 PDF KSCI

Maternal Exposure to Environmental Tobacco Smoke(ETS) and Pregnancy Outcome(low birth weight or preterm baby) in Prospective Cohort Study (임산부 간접흡연과 저체중아 및 조산아 출생에 관한 코호트 연구)

  • Lee, Bo-Eun;Hong, Yun-Chul;Park, Hye-Sook;Lee, Jong-Tae;Kim, Jeong-Youn;Kim, Young-Joo;Kim, Sang-Hyun;Kang, Jung-Goo;Kim, Joo-Oh;Ha, Eun-Hee
    • Journal of Preventive Medicine and Public Health
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    • v.36 no.2
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    • pp.117-124
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    • 2003

  • Objectives : This study was performed to examine the relationship between maternal exposure to environmental tobacco smoke (ETS) and pregnancy outcomes (low birth weight or preform baby) in a prospective cohort study. Methods : We made a pregnant women's cohort, and followed the pregnancy outcomes, between May 1st 2001 and August 31st 2002. We surveyed 2,250 women who visited our hospital during their 35th gestational week, with a self-administered questionnaire. The final total of mother-infant pairs analyzed in this study was 1,712. We used a multiple logistic regression analysis to analyze the effect of maternal ETS on the incidence of preform or low birth weight, and a linear regression analysis for the birth weight and gestational age. Results : Higher exposure to ETS (>=1 hours/day) during pregnancy was more negatively associated with the gestational age and birth weight, than no exposure to ETS (no or less than 1 hour). Maternal exposure to ETS was associated with preform baby(adjusted odds ratio (AOR) 1.7; 95% confidence interval (CI) 0.9, 3.3) and low birth weight (AOR 2.3; 95% CI 0.9, 5.5). In addition, we found that maternal ETS may reduce the birth weight by 70g after adjusting for potential confounding factors. Conclusions : This study suggests that maternal exposure to ETS during pregnancy may increase the frequency of low birth weights and preform births.

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