• 한국자동차공학회논문집
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• 제13권4호
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• pp.174-181
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• 2005

In order to investigate the behavior of fatigue crack growth of SiC-particulate- reinforced Al-Si alloy composites, fatigue tests using single edge notched tension(SENT) specimens were performed. Composite materials were manufactured by using both permanent die casting and extrusion processes with different volume fractions of $10\%\;and\;20\%$. $SiC_p-reinfurced$ Al-Si composites showed the increased levels of threshold stress intensity factor range, ${\Delta}K_{th}$, for the increased volume fractions of SiC particles, which implies the increased fatigue crack growth resistance at the threshold or low ${\Delta}K$ levels, compared to the unreinforced Al-Si alloy. In the Paris region, however, the composites showed the increased rate of crack growth resulting in the unfavorable effects on the fatigue crack growth resistance. Critical stress intensity factor range at unstable crack growth leading to final fracture decreased as the volume fraction of SiC particle increased, because of the reduced fracture toughness of the composites. Extruded materials showed higher threshold and critical values than the cast materials.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.349-354
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• 1999

Specialty cellulose fibers processed for the reinforcement of concrete offer relatively high levels of elastic modulus and bond strength. The hydrophilic surfaces of specialty cellulose fibers facilitate their dispersion and bonding in concrete. Specialty cellulose fibers have small effective diameters which are comparable to the cement particle size, and thus promote close packing and development of dense bulk and interface microstructure in the matrix. The relatively high surface area and the close spacing of specialty cellulose fibers when combined with their desirable mechanical characteristic make them quite effective in the suppression and stabilization of microcracks in the concrete matrix. The properties of fresh mixed specialty cellulose fiber reinforced concrete and the contribution of specialty cellulose fiber to the restrained shrinkage crack reduction potential of cement composites at early age and theirs evaluation are presented in this paper. Results indicated that specialty cellulose fiber reinforcement showed an ability to reduce the total area significantly (as compared to plain concrete and polypropylene fiber reinforced concrete.

• 한국구조물진단유지관리공학회 논문집
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• 제24권5호
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• pp.95-102
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• 2020

이 연구에서는 입경이 큰 골재를 사용하면서 2% 이상의 인장변형률 성능을 나타내는 고연성 PE 섬유보강 시멘트 복합체 개발을 목적으로 골재의 크기와 입도분포에 따른 고연성 섬유보강 시멘트 복합체의 인장거동 특성을 살펴보고자 하였다. 0.6 mm 이하의 입경들로 구성된 규사를 사용한 배합을 기준으로 최대입경 2.36 mm, 4.75 mm, 5.6 mm, 6.7 mm의 강모래 및 강자갈을 사용한 배합을 비교하여 성능평가를 실시하였다. 골재의 입도분포는 수정 A&A 모델에 기반한 최적입도분포곡선에 가깝도록 세분화된 입경별 혼합비율을 조절하였다. 직접인장실험을 통해 구한 인장거동은 모든 배합에서 뚜렷한 인장변형률 경화 거동을 보였다. 골재 입경별 혼합비율을 조절하여 입도분포가 최적곡선에 가깝도록 한 경우에는 모든 배합에서 규사를 사용한 경우보다 높은 인장변형률 성능을 나타내었다. 또한 골재의 최대입경이 커서 입도분포가 넓을수록 높은 인장변형률 성능을 보였으며, 최대입경 5.6 mm, 6.7 mm의 굵은 골재를 포함하는 경우 각각 4.83%와 5.89%의 매우 높은 인장변형률 성능을 나타내었다. 이 연구를 통해 적절한 입도분포 조절을 통해 굵은 골재를 사용하면서도 고연성 섬유보강 시멘트 복합체의 제조가 가능함을 보였다.

• 대한기계학회논문집A
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• 제25권1호
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• pp.25-31
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• 2001

The theoretical modeling to predict the modulus of elasticity by the shape memory effect of dispersed particles in a metal matrix composite was studied. The modeling approach is based on the Eshelbys equivalent inclusion method and Mori-Tanakas mean field theory. The calculation was performed on the TiNi particle dispersed Al metal matrix composites(PDMMC) with varying volume fractions and prestrains of the particle. It was found that the prestrain has no effect on the Yonugs modulus of PDMMC but the volume fraction does affects it. This approach has an advantage of definite control of Youngs modulus in PDMMCs.

• 한국분말재료학회지
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• 제7권1호
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• pp.35-41
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• 2000

Al2O3$.$SiC particle was prepared was prepared by the self-propagting high temperature sYthesis(SHS) process from a mixture of SiO2, Al and C powders, The fabricated Al2O3$.$SiC particle was applied to 2024Al/(Al2O3$.$SiC)pcomposite as a reinforcement. Aluminum matix composites were fabricares by the powder extrusion method using the synthesized Al2O3$.$SiC particle and commercial 2024Al powder. Theoptimum preparation conditions for Al2O3$.$SiC partticle by SHS process were described. The influence of the Al2O3$.$SiC voiume fraction on the mechanical was composite was also discussed. Despite adiabatic temperature was about 2367K, SHs reaction was completed not by itself, but by using pre-heating. Mean particle size of final particle synthesized was 0.73 ${\mu}$m and most of the particle was smaller than 2${\mu}$m. Elastic modulus and tensile strength of the composite increased with increase the volume fraction of reinforcement but, tensile strength depreciated at 30 vol% of reinforcement.

• 한국재료학회지
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• 제11권5호
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• pp.372-377
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• 2001

Part I에서 도출된 기초 식을 적용하여 입자 분산 강화형, 섬유 강화형 및 적층형 복합재료의 유효탄성제수 및 열팽창계수를 산정 하였다. 일방향 섬유 강화 복합재료의 경우 섬유의 유효 축비 (aspect ratio)가 고려되었으며, 유효 탄성계수는 다른 연구 결과들과 비교하였다. 입자 분산 강화형 복합재료의 유효 체적탄성률 및 전단 탄성률은 Korner의 표식 및 Hanshin과 Shtrikman의 하한치 (lower bounds)와 일치하고 있다. 일방향 섬유 강화 복합재료에서는 6개, Hanshin과 Rosen의 모델에 나타낸 4개의 독립 탄성계수와 일치하고 있다.

• 한국주조공학회지
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• 제20권4호
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• pp.254-259
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• 2000

Metal matrix composites(MMCs) reinforced with hard particles have many potential application in aerospace structures, auto parts, semiconductor package, heat resistant panels, wear resistant materials and so on. In this work, the effect of SiC partioel sizes(50 and 100 ${\mu}m$) and additional elements such as Si, Cu and Ti on the microstructure and the wear property of $Al-5Mg-X(Si,Cu,Ti)/SiC_p$ composites produced by pressureless infiltration method have been investigated using optical microscopy, scanning eletron microcopy(SEM) with EDS(energy dispersive spectrometry), hardness test, X-ray diffractometer(XRD) and wear test. In present study, the sound $Al-5Mg-X(Si,Cu,Ti)/SiC_p$(50 and 100 ${\mu}m$) composites were fabricated by pressureless infiltration method. The $Al-5Mg-0.3Si-O.1Cu-O.1Ti/SiC_p$ composite with $50 {\mu}m$ size of SiC particle has higher hardness and better wear property than any other composite with $100{\mu}m$ size of SiC particle produced by pressureless infiltration method. The hardness and wear property of $Al-5Mg/SiC_p$(50 and 100 ${\mu}m$) composites were enhanced by the addition of Si, Cu and Ti in Al-5%Mg matrix alloy.

• Journal of Welding and Joining
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• 제18권5호
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• pp.98-104
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• 2000

Aluminum alloys are being employed in automobile parts as strive to reduce overall vehicle weight to meet demands for improved fuel economy and reduction in vehicle emissions. Al-based composites reinforced with ceramic ($Al_2O_3,\;SiC,\;TiC\;and\;B_4C$) applications in a variety of components in automotive engines, such as liners, where the tribological properties of the material are important. In this study, Al-base composites reinforced with TiC particle powders has been developed for producing plasma spray coatings. The composite plasma spray powders were prepared Al-13Si-3Mg(wt%) alloy with TiC(40, 60 and 80wt%) particles ($0.2~5{\mu}textrm{m}$) by drum type ball milling. The composite powders ($36~76{\mu}textrm{m}$) were sprayed with plasma torch. Plasma sprayed coatings were heat-treated at $500^{\circ}C$ for 3 hours. The wear resistances of the plasma sprayed coatings were found to decrease with increasing TiC content and improved with heat treatment. AlSiMg-40% TiC heat-treated coatings were showed the best wear resistance in this study.

• Composites Research
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• 제33권2호
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• pp.81-89
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• 2020

본 리뷰 논문에서는 최근에 연구된 평균장 균질화법을 이용한 다양한 물성치 예측 연구의 동향에 대해 소개한다. 유효 강성 예측에 사용되는 기존의 균질화법을 소개하고 이를 확장하여 유효 열/전기 전도성 및 유전 상수를 예측하는 방법을 소개한다. 압전 및 열전과 같이 2개의 물리현상이 중첩된 다중 물리 현상의 구성방정식은 훅 법칙과 같이 단순한 선형 형태로 변환하여 복합재의 유효 물성치를 예측하는 연구를 소개하고 마지막으로 복합 재료의 유효 물성치를 예측하기 위한 일반화된 식을 제시하고 유한 요소 해석과 비교한 검증/연구를 소개한다.

• 한국항공우주학회지
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• 제46권7호
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• pp.535-541
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• 2018

본 연구에서는 입자강화 복합재료의 파괴거동을 평가하기 위해 쐐기분열시험을 수행하였다. 균열 저항성을 분석하기 위해 균열선단열림변위(CTOD)와 균열선단열림각도(CTOA)를 이용하였다. 사용된 입자강화 복합재료는 특성상 온도와 하중속도에 영향을 많이 받기 때문에 다양한 온도($-60^{\circ}C{\sim}50^{\circ}C$)와 하중속도(5~500mm/min)조건에서 시험을 수행하였다. 또한 균열선단에 대한 변형률장을 분석하기 위해 디지털 이미지 상관법(DIC)을 이용하였다. 시험결과 파괴에너지는 온도가 감소할수록 증가하였으며, 하중속도가 증가할수록 균열저항성이 증가하였다.