• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.31-37
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• 2000

Metal matrix composites(MMCs) are rapidly becoming one of the strongest candidates for structural materials for many high temperature application. Among the high temperature environment, thermal shock is known to cause significant degradation in most MMC system. Therefore, the nondestructive evaluation on thermal shock damage behavior of SiC/A16061 composite has been carried out using ultrasonic surface and SH-waves. For this study, Sic fiber reinforced metal matrix composite specimens fabricated by a squeeze casting technique were thermally cycled in the temperature range 25~$400^{\circ}C$ up to 1000 cycles. Three point bend test was conducted to investigate the effect of thermal shock damage on mechanical properties. The relationship between thermal shock damage behavior and the change of ultrasonic velocity and attenuation were discussed by considering SEM observation of fracture surface.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.219-222
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• 2004

The effects of short fiber and particle hybrid reinforcement on fatigue crack propagation behaviors in aluminum matrix composites have been investigated. Single and hybrid reinforced 6061 aluminum containing same 20 $Al_2O_3\;volume\%$ with four different constituent ratios of short fibers and particles were prepared by squeeze casting method and tested to check the near-threshold and stable crack growth behavior. The fatigue threshold of the composites increased with portion of particle contents and showed the improved crack resistance especially in low stress intensity range. Addition of particle instead of short fiber also increased fracture toughness due to increase of inter-reinforcement distance. These increase in both fatigue threshold and fracture toughness eventually affected the fatigue crack growth behavior such that the crack growth curve shift low to high stress intensity factor value. Overall experimental results were shown that particle reinforcement was enhanced the fatigue crack resistance over the whole stress intensity factor range.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.581-593
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• 1990

A semi-solid alloy in which solid and liquid phase are co-existing is obtained by strirring of Al7075 molten metal. A semi-solid alloy is dependent on the corresponding temperature within the solid-liquid range, and the process parameters should be controlled accurately to obtain the homogeneous semi-solid alloy. The possibility o homogeneous fiber-reinforce aluminum alloy by addition of $Al_{2}$O$_{3}$ short fibers with vigorous agitation was investigated. The billet of composite materials was fabricated by squeeze casting, and homogeneous dipersion state of fibers in billet of fabricated metal matrix composites was observed. A slurry of semi-solid short fiber metal matrix composites is used in the direct rolling process, and this process showed the fabrication possibility of metal matrix composite sheets. The fabricated sheet was tested regarding vickers hardness, elongation and micro-structure. It has become clear that mashy state processing and working are very useful to obtain parts of composites material closed to near net shape.

• Journal of the KSME
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• v.32 no.1
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• pp.28-38
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• 1992

음향 방출법은 기존의 비파괴 시험보다 여러 가지 면에서 장점을 가지고 있고 또 그 응용범위는 매우 넓다. 그러나 아직 우리 나라에서는 그 사용 예가 많지 않다. 이 글에서는 음향 방출법에 대한 개요와 음향 방출법을 이용한 복합재료와 금속재료의 균열 거동 해석 예를 저자의 연구 결과를 중심으로 소개하고자 한다.

• Journal of the KSME
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• v.28 no.3
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• pp.216-225
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• 1988

고성능 복합재료는 그 제조 공정이 다양하고 공정의 개념이 기존 금속 재료와는 크게 다르며, 많은 열 공학 및 금속 재료와는 크게 다르며, 많은 열 공학 및 유체공학적인 문제를 수반하고 있다. 특히 최적 공정의 선택이 가장 큰 관심의 대상이므로 공정의 modeling에 대한 연구가 많이 이루어지고 있으며, 이러한 modeling을 통하여 고성능 복합재료 제조 공정에서의 문제점을 보다 잘 이해할 수 있고 제조 공정의 최적화에 이용할 경우 비용이 많이 들고 시간이 오래 걸 리는 실험적인 방법을 많은 부분 대치할 수 있어 새로운 기지재료가 소개되었을 경우의 그 제조 공정의 결정에 있어 시간과 비용을 대폭 절감시킬 수 있다. 앞으로 소재의 기능화, 경량화 추 세에 힘입어 복합재료의 수요는 계속 늘어날 전망이어서 새로운 공업용 소재로서의 복합재료에 대한 공학적인 이해가 필요하며, 특히 기존의 재료 제조 공정과는 비교적 색다른 복합재료 제조 공정에 대한 보다 넓은 이해가 필요할 것이다.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.228-232
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• 2002

본 연구에서는 다목적 실용위성 2호기에 적용된 금속 구조물 중 알루미늄 샌드위치 패널 구조인 탑재체 플랫폼과 튜브 스트럿(tube strut) 구조에 복합재료 응용기술을 적용하였다. 복합재료 구조로의 대체 설계에서도 관성하중 및 음향진동등과 같은 극심한 발사환경과 더불어 운용하게 될 우주 열환경을 고려하였다. 연구의 목적은 금속소재보다 비강도, 비강성이 우수한 복합재료를 위성 구조물에 사용함으로써 무게를 경량화함에 있다.

• Korean Journal of Materials Research
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• v.6 no.11
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• pp.1090-1098
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• 1996

개조한 가스 금속 아아크 용접공정을 이용하여 SiC/AI 금속기 복합재료를 제조하고 그 특성을 조사하였다. AI 모재위에 강화입자의 크기와 부피분율을 변화하여 다양한 SiC/AI 복합재료층을 제조하였고, 만들어진 복합재료층의 특성은 미세조직관찰과 미소경도시험을 통하여 이루어졌다. 복합재료층의 두께는 약 7-8mm로 측정되었고 균일한 강화입자의 분포도를 얻을 수 있었다. 분산입자의 부피분률은 Ar가스의 유량에 의하여 조절하였고 분산입자의 부피분률이 증가하고 크기가 작아짐에 따라 기지의 수지상 응고조직은 더욱 미세화되었다. 복합재료의 부피경도는 분산입자의 부피분률이 감소함에 따라 낮아졌으나 입자 크기에는 크게 변화가 없는 것으로 나타났다.

• 기계와재료
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• v.2 no.4 s.6
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• pp.82-88
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• 1990

• Composites Research
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• v.16 no.3
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• pp.1-8
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• 2003

Densification occurs by the inelastic flow of the matrix materials during the consolidation processes at high temperature for MMCs, and the results depend on many process conditions such as applied pressure, temperature and volume fraction of fiber and matrix materials. This is particularly important in titanium matrix composites since material failure may occur by either the applied conditions or microstructural parameters through the processes, and thus a generic model based on micro-mechanical approaches enabling the evolution of density over time to be predicted has been developed. The mode developed is then implemented into FEM so that practical process simulation has been carried out. Further the experimental investigation of the consolidation behavior of SiC/Ti-6Al-4V composites using vacuum hot pressing has been performed, and the results obtained are compared with the model predictions.

• Composites Research
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• v.23 no.2
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• pp.10-16
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• 2010

$Al_2O_3$ fiber and SiC particle hybrid metal matrix composites (MMCs) were manufactured by squeeze casting method investigated for their tribological properties. The pin specimens had different ratios of fiber to particle content but their total weight fraction was constant at 20 wt. %. Tribological tests were performed with a pin-on-disk friction and wear tester. The investigation of the dry tribological characteristics of hybrid MMCs were carried out at room temperature and elevated temperature of$100^{\circ}C$ and$150^{\circ}C$. The morphologies of worn surfaces were examined by scanning electron microscope (SEM) to observe tribological characteristics and investigate wear behavior. The results revealed that the wear resistance improved with the content of SiCp increased of the planar random (PR) MMCs at room temperature. At the elevated temperature, it revealed that the wear resistance of normal (N) MMCs was superior to that of the PR-MMCs due to PR-fibers were easily pulled out holistically from the worn surface. Meanwhile, the coefficient of friction decreased with the temperature increasing.