• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제31회 춘계학술대회
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• pp.173-179
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• 2000

The friction and wear characteristics of brake friction materials reinforced with aramid fiber, carbon fiber, glass fiber, and potassium titanate whiskers were investigated using a pad-on-disk type friction tester. In particular, the morphology of rubbing surfaces was carefully investigated to correlate the friction performance and properties of transfer films. The aramid fiber reinforced specimen showed severe oscillation of friction coefficient at low speed and low applied pressure. The carbon fiber reinforced specimen showing better friction stability exhibited uniform and stable transfer film than any other specimens. The glass fiber reinforced specimen showed unstable friction changes at high speed and high-applied pressure and the non-uniform transfer film was observed in both friction material and rotor surface. The potassium titanate whiskers reinforced specimen showed stable coherent transfer film. The wear test exhibited the potassium titanate whiskers reinforced specimen was lowest in wear amount and glass fiber reinforced specimen showed the severe wear.

• 한국농공학회논문집
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• 제55권4호
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• pp.29-35
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• 2013

The objective of the current study is to evaluate the effects depending on the types of reinforcing fibers being influential in view of mechanical properties and impact resistance of hybrid fiber reinforced concrete (HFRC) for applications to precast concrete structure. Hybrid fibers applied therefor were three types such as PP/MSF (polypropylene fiber+macro synthetic fiber), PVA/MAF (polyvinyl alcohol fiber+MSF) and JUTE/MSF (natural jute fiber+MSF), where the volume fraction of PP, PVA and natural jute was applied with 0.2 %, respectively, while based on 0.05 % volume fraction of MSF. The HFRC was tested for slump, compressive strength, flexural strength and impact resistance. The test result demonstrated that mixture of such hybrid fibers improve compressive strength, flexural strength and impact resistance of concrete. Moreover, it was found that HFRCs to which hydrophilic fibers, i.e. PVA/MSF and JUTE/MSF, were mixed show more improved features that HFRC to which non-hydrophilic fiber, i.e. PP/MSF was mixed. Meanwhile, the finding that PVA/MSF HFRC exhibited better performance than JUTE/MSF HFRC was attributed from the former having higher aspect ratio than that of the latter.

• Structural Engineering and Mechanics
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• 제22권3호
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• pp.311-330
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• 2006

Standard compression tests of steel fiber reinforced concrete (SFRC) cylinders are conducted to formulate compressive stress versus compressive strain relationship of SFRC. Axial pullout tests of SFRC specimens are also conducted to explore its tensile stress strain relationship. Cover concrete spalling and reinforcement buckling models developed originally for normal reinforced concrete are modified to extend their application to SFRC. Thus obtained monotonic material models of concrete and reinforcing bars in SFRC members are combined with unloading/reloading loops used in the cyclic models of concrete and reinforcing bars in normal reinforced concrete. The resulting path-dependent cyclic material models are then incorporated in a finite-element based fiber analysis program. The applicability of these models at member level is verified by simulating cyclic lateral loading tests of SFRC columns under constant axial compression. The analysis using the proposed SFRC models yield results that are much closer to the experimental results than the analytical results obtained using the normal reinforced concrete models are.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.667-671
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• 2004

The purpose of this paper is to study on the construction of environmentally friendly roadbed by reinforcing type soil solidification agent. The soil amendment agent used in this study is friendly to the environment, and has a function of soil-cement-agent solidification. The soil amendment agent was admixed with reinforced fiber material for enhancement of strength and durability of roadbed. The project of trial field test of roadbed construction with special reinforcing soil treatment agent was performed in Gyunggido on December 2003. A series of field and laboratory experiments including unconfined compressive strength, permeability were carried out to investigate the physical and mechanical characteristics of solidified roadbed treated by this reinforced solidifying agent. The results of this research showed that the roadbed using normal and poor soil could be efficiently constructed by treatment of this reinforcing type solidification agent admixed with fiber material.

• Computers and Concrete
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• 제3권6호
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• pp.389-400
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• 2006

This paper presents the investigations towards developing a better understanding on the contribution of steel fibers on the tensile strength of high-performance fiber reinforced concrete (HPFRC). An extensive experimentation was carried out with w/cm ratios ranging from 0.25 to 0.40 and fiber content ranging from zero to 1.5 percent with an aspect ratio of 80. For 32 concrete mixes, flexural and splitting tensile strengths were determined at 28 days. The influence of fiber content in terms of fiber reinforcing index on the flexural and splitting tensile strengths of HPFRC is presented. Based on the test results, mathematical models were developed using statistical methods to predict 28-day flexural and splitting tensile strengths of HPFRC for a wide range of w/cm ratios. The expressions, being developed with strength ratios and not with absolute values of strengths and are applicable to wide range of w/cm ratio and different sizes/shapes of specimens. Relationship between flexural and splitting tensile strengths has been developed using regression analysis and absolute variation of strength values obtained was within 3.85 percent. To examine the validity of the proposed model, the experimental results of previous researchers were compared with the values predicted by the model.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 춘계학술발표대회 논문집
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• pp.117-120
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• 2003

Electro-micromechanical techniques were applied using four-probe method for carbon nanotube (CNT) or nanofiber (CNF)/epoxy composites with their content. Carbon black (CB) was used to compare with CNT and CNF. The fracture of carbon fiber was detected by nondestructive acoustic emission (AE) relating to electrical resistivity for double-matrix composites test. Sensing for fiber tension was performed by electro-pullout test under uniform cyclic strain. The sensitivity for fiber damage such as fiber fracture and fiber tension was the highest for CNT/epoxy composites, and in CB case they were the lowest compared with CNT and CNF. Reinforcing effect of CNT obtained from apparent modulus measurement was the highest in the same content. The results obtained from sensing fiber damage were correlated with the morphological observation of nano-scale structure using FE-SEM. The information on fiber damage and matrix deformation and reinforcing effect of carbon nanocomposites could be obtained from electrical resistivity measurement as a new concept of nondestructive evaluation.

• Advances in materials Research
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• 제4권2호
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• pp.97-111
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• 2015

Polypropylene short fiber (PP)-clay particulate-epoxy ternary composites were prepared by reinforcing PP short fiber and clay particles in the range of 0.1 phr to 0.7 phr into epoxy resin. Prepared hybrid composites were characterized for their mechanical, thermal and flame retardant properties. The obtained results indicated an increase in impact resistance, tensile strength, flexural strength and Young's modulus to an extent (up to 0.5 phr clay and 0.5 phr PP short fiber) and then decreases as the reinforcing phases are further increased. The thermal stability of these materials are found to increase up to 0.2 phr clay and 0.2 phr PP addition, beyond which it is decreased. Addition of clay is found to have the negative effect on epoxy-PP short fiber composites, which is evident from the comparison of mechanical and thermal properties of epoxy-0.5 phr PP short fiber composite and epoxy-0.5 phr PP short fiber-0.5 phr clay composite hybrid. UL-94 tests conducted on the composite hybrids have showed a reduction in the burning rate. Morphological observations indicated a greater fiber pull with the addition of clay. The performed tests in the present study indicated that materials under investigation have promising applications in construction, agriculture and decorative purposes.

• 한국철도학회논문집
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• 제10권2호
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• pp.186-194
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• 2007

This study was performed to compare the load-carrying capacities of the reinforced concrete structure between the carbon fiber adhesion reinforcement method and the external post-tensioning method and further estimate the effective stress of the reinforced material by analyzing the experimental reinforcing effect of each method and the behavior resulting from each method. As a result, it was found out that the effective stress of the carbon fiber reinforcement according to the carbon fiber adhesion reinforcement method had an unexpected value, and also, bearing of the stress was found to be far from sharing thereof. That is to say, while the carbon fiber was bearing the whole stress to some limits, it got to be momentarily ruptured as soon as it went beyond such limits. On the other hand, the external post-tensioning method has the advantage of inducing an initial effective stress by introducing a strain, and thus, it was found that behavior or bearing of the stress was also found to be a solid behavior of the steel wire. This method was also found to be more efficient and excellent than the carbon fiber adhesion reinforcement method in the reinforcing effect or securing the effective stress. Accordingly, we were to discuss the effective stress as comparatively examined, focusing on deriving of the more enhanced reinforcing effect on the basis of the experiment to which the field characteristic is added.

• 공업화학
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• 제16권3호
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• pp.361-365
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• 2005

$O_2$, $H_2O$, acrylic acid, diaminocyclohexane 등의 저온 플라즈마를 이용하여 시멘트 보강용 탄소 섬유 표면을 친수성으로 개질한 다음, 이에 대한 효과를 살펴보았다. 물과의 접촉각이 $75{\sim}80^{\circ}$ 정도로 소수성이던 표면이 친수성으로 변하여 접촉각이 $10^{\circ}$ 이하로까지 낮아졌으며, 이에 따라 흡습성 및 수용액에서 분산성이 크게 향상되었다. 또한, 섬유표면의 제타 포텐셜이 변하여 시멘트와 정전기적 인력이 향상됨으로써 시멘트의 결착도 향상과 함께 시멘트와의 결합이 57~124%까지 향상되었다.

• 한국구조물진단유지관리공학회 논문집
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• 제5권2호
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• pp.121-128
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• 2001

Reinforced concrete frame buildings in regions of low to moderate seismicity are typically designed only for gravity loads with non-seismic detailing provisions of the code. These buildings possess strong beam-weak column, which brings about the brittle structural performance like the column sidesway failure mechanism during the strong lateral load. The objective of this paper is to enhance the column strength and deformation capacity for reconfiguring the structural failure mode by averting a column soft-story collapse and moving to a more ductile beam-sides way mechanism suing new reinforcing materials. Aramid fiber sheet and reinforcing rod-composite materials was used for this purpose. The column was modeled by the 2/3 scale experimental specimen retested. According to the concept of the capacity design, the damaged column was strengthened by the column jacketing using new reinfocing materials such as rod-composite materials. In conclusion, the improvement of the flexural strength is observed and the capacity of the energy dissipation and the ductility is enhanced, too.