• 한국분말재료학회지
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• 제19권2호
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• pp.122-126
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• 2012

The Fe-based self-fluxing alloy powders and TiC particles were ball-milled and subsequently compacted and sintered at various temperatures, resulting in the TiC particle-reinforced Fe self-fluxing alloy hybrid composite, and the microstructure and micro-hardness were investigated. The initial Fe-based self-fluxing alloy powders and TiC particles showed the spherical shape with a mean size of approximately 80 ${\mu}m$ and the irregular shape of less than 5 ${\mu}m$, respectively. After ball-milling at 800 rpm for 5 h, the powder mixture of Fe-based self-fluxing alloy powders and TiC particles formed into the agglomerated powders with the size of approximately 10 ${\mu}m$ that was composed of the nanosized TiC particles and nano-sized alloy particles. The TiC particle-reinforced Fe-based self-fluxing alloy hybrid composite sintered at 1173 K revealed a much denser microstructure and higher micro-hardness than that sintered at 1073 K and 1273 K.

• Steel and Composite Structures
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• 제27권1호
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• pp.95-108
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• 2018

A new composite reinforced method, namely self-compacting concrete filled circular CFRP-steel jacketing, was proposed in this paper. Experimental tests on eight RC square short columns reinforced with the new composite reinforced method and four RC square short columns reinforced with CFS jackets were conducted to investigate their eccentrically compressive behaviour. Nine reinforced columns were subjected to eccentrically compressive loading, while three reinforced columns were subjected to axial compressive loading as reference. The parameters investigated herein were the eccentricity of the compressive loading and the layer of CFRP. Subsequently, the failure mode, ultimate load, deformation and strain of these reinforced columns were discussed. Their failure modes included the excessive bending deformation, serious buckling of steel jackets, crush of concrete and fracture of CFRP. Moreover, these reinforced columns exhibited a ductile failure globally. Both the eccentricity of the compressive loading and the layer of CFRP had a significant effect on the eccentrically compressive behaviour of reinforced columns. Finally, formulae for the evaluation of the ultimate load of reinforced columns were proposed. The theoretical formulae based on the ultimate equilibrium theory provided an effective, acceptable and safe method for designers to calculate the ultimate load of reinforced columns under eccentrically compressive loading.

• Composites Research
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• 제28권4호
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• pp.197-203
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• 2015

폴리프로필렌 기반 자기보강 복합재는 기지재와 보강재가 동일한 소재로 구성되어 기존 섬유강화 복합재와 달리 섬유와 기지재의 분리없이 바로 재활용이 가능할 뿐 아니라 폴리프로필렌 수준까지 저 비중화가 가능한 고분자 복합재이다. 본 연구에서는 더블벨트 라미네이터 공정기술을 이용하여 압력, 온도, 냉각조건과 같은 공정 변수가 폴리프로필렌으로 제조된 자기보강 복합재의 인장 물성에 미치는 영향을 연구하였다. XRD, DSC를 이용하여 결정구조의 변화에 따라 인장 탄성계수는 0.2~1.2 GPa로 약 6배까지 향상되는 것을 확인하였다. SEM 분석을 통해 함침 정도를 확인함으로써 자기보강 복합재의 함침 후 형상 변화 또한 고찰하였다.

• Advances in aircraft and spacecraft science
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• 제3권1호
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• pp.29-43
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• 2016

Composite materials are rapidly gaining popularity as an alternative to metals for structural and load bearing applications in the aerospace, automotive, alternate energy and consumer industries. With the advent of thermoplastic composites and advances in recycling technologies, fully recyclable composites are gaining ground over traditional thermoset composites. Stamp forming as an alternative processing technique for sheet products has proven to be effective in allowing the fast manufacturing rates required for mass production of components. This study investigates the feasibility of using the stamp forming technique for the processing of thermoplastic, recyclable composite materials. The material system used in this study is a self-reinforced polypropylene composite material (Curv$^{(R)}$). The investigation includes a detailed experimental study based on strain measurements using a non-contact optical measurement system in conjunction with stamping equipment to record and measure the formability of the thermoplastic composites in real time. A Design of Experiments (DOE) methodology was adopted to elucidate the effect of process parameters that included blank holder force, pre heat temperature and feed rate on stamp forming. DOE analyses indicate that feed rate had negligible influence on the strain evolution during stamp forming and blank holder force and preheat temperature had significant effect on strain evolution during forming.

• Journal of Mechanical Science and Technology
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• 제20권3호
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• pp.310-318
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• 2006

In this study, we investigate the feasibility of in-situ crack propagation by using a double cleavage drilled compression (DCDC) specimen showing a slow crack velocity down to 0.03 mm/s under 0.01 mm/s of displacement control. Finite element analysis predicted that the DCDC specimens would show at least 4.3 fold delayed crack initiation time than conventional tensile fracture specimens under a constant loading speed. Using DCDC specimens, we were able to observe the in-situ crack propagation process in a particle reinforced transparent polymer composite. Our results confirmed that the DCDC specimen would be a good candidate for the in-situ observation of the behavior of particle reinforced composites with slow crack velocity, such as the self-healing process of micro-particle reinforced composites.

• 콘크리트학회논문집
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• 제20권3호
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• pp.369-374
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• 2008

두 가지 형식의 전도성 재료를 선정하고, 이들 재료를 모르타르, 무근콘크리트 및 철근콘크리트 시험체에 각각 배합 혼입한 후, 이들 구조체에 대해 파괴예측 자기진단 재료로서의 적용 특성을 검토하였다. 본 연구에서는 자기진단 (스마트) 성능을 부여하기 위해 코크스와 미분쇄 (微粉碎) 탄소섬유분말을 전도성 재료로 선정하였다. 각 휨 하중 재하단계에서 이들 시험체에 대한 균열발생 전후의 전기저항값과의 변화 특성 시험을 통해, 이들 각 측정 인자 (전기저항, 균열, 휨 하중)의 상호 연관성을 검토하였다. 그 결과, 코크스와 미분쇄 탄소섬유분말의 전도성 재료는 복합모르타르, 무근콘크리트, 철근콘크리트 시험체의 휨 파괴 예측 자기진단에 사용이 가능함을 알 수 있었다.

• 소성∙가공
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• 제22권3호
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• pp.150-157
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• 2013

Fiber metal laminates (FMLs) are layered materials comprised of thin metal sheets and fiber reinforced plastic (FRP). This paper presents the numerical study of the formability enhancement of FMLs composed of an aluminum alloy and self-reinforced polypropylene (SRPP) composite. In this study, a numerical simulation based on finite element (FE) modeling is proposed to evaluate the formability of FMLs using ABAQUS/Explicit. The FE model, which included a single layer of solid and shell elements to model the blank, used discrete layers of the solid element with a contact model and shell elements with a friction based model for the aluminum alloy-composite interface conditions. This method allowed the description of each layer of FMLs and was able to simulate the interaction between the layers. It is noted through this research that the proposed numerical simulation described properly the formability enhancement of the FMLs and the simulation results showed good agreement with experimental results.

• 대한금속재료학회지
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• 제49권12호
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• pp.1001-1004
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• 2011

The formation of TiC and $Al_2O_3$ particles based on the self-combustion reaction of the $Al-TiO_2-C-CuO$ system in an Al alloy melt was investigated. With an adequate amount of CuO in the system, a spontaneous reaction occurred within the Al alloy melt at $850^{\circ}C$ and thereafter was self-maintained, producing an Al matrix composite reinforced with thermodynamically stable TiC and $Al_2O_3$ particles. TiC and $Al_2O_3$ particles contributed to a considerable increase in the strength and stiffness, demonstrating the feasibility of this method as a practical application for structural parts.

• 한국해양공학회지
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• 제28권4호
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• pp.351-355
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• 2014

Today, carbon fibers are used as heating elements. Carbon fibers are generally used to reinforce composite materials because they are lightweight and have a high strength and modulus. Carbon fiber reinforced composite materials are used for aerospace, automobile, and wind turbine blade applications. This work explored the possibility of using carbon fiber reinforced composite materials as self heating materials. The temperatures of the carbon fiber reinforced composites were measured. These results verified that the carbon fiber reinforced composite materials could be used as heating elements. A glass fiber was laminated using various methods. The thermal characteristics of the composites were evaluated. This confirmed that the generation of heat varied according to the lamination thicknesses of the carbon fiber and glass fiber. As the number of carbon fiber laminations increased, the heat-generating temperature increased. In contrast, as the number of glass fiber laminations increased, the amount of heat decreased. The generation of heat and ability to remain warm could be controlled by controlling the carbon fiber and glass fiber laminations.

• Composites Research
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• 제31권5호
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• pp.221-226
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• 2018

변형률 속도 $100s^{-1}{\sim}10000s^{-1}$ 범위에서 사용되는 홉킨스바(SHPB)는 재료의 동석 거동 특성을 확인하기 위해 가장 널리 사용되는 장치이다. SHPB 시험은 입력봉 및 전달봉에서 측정된 변형률을 사용하여 시험편의 응력, 변형률 및 변형률 속도를 얻을 수 있는 응력파 전달 이론을 기반으로 한다. 본 연구에서는 고 변형률 속도에서 폴리프로필렌 자기보강 복합재료(SRPP)의 동적 특성을 얻기 위해 직접 SHPB를 설계 및 제작하였다. 또한 본 연구를 통해 제작된 SHPB에서 얻은 변형률 데이터의 신뢰성 확보를 위하여 Digital Image Correlation (DIC)를 통해 얻은 변형률 데이터와의 비교를 진행하였다. 이는 SRPP 시편의 고속 압축 시험을 통해 이루어 졌으며 SHPB를 통하여 얻은 데이터와 DIC를 통해 얻은 변형률 데이터의 유사함을 확인하였고 이를 통하여 장비의 신뢰성을 검증하였다.