• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.2
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• pp.200-206
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• 1992

The effect of fiber diameter and gauge length on pull-out test for the interfacial properties in fiber reinforced resin composites have been investigated and these results have been arranged as statistical analysis. The fiber and matrix resins used for this study were stainless steel fiber (SUS316) and carbon fiber (high strength type), epoxy and high density polyethylene resin. From this study, it has been found that shear strength are constant regardless of gauge length of pull-out test and coefficient of variation depend on fiber diameter. In addition, it has been found that the interfacial shear strength decreased with the increasing fiber diameter, and in all case, Weibull parameter (m) has approximately 1.2/C.O.V.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.656-659
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• 1993

The failure phenomenon of Dual Basalt Fibers Reinforced Epoxy Composites(DFC) under tensile load was studied using acoustic emission(AE) technique. AE amplitude and AE energy were mainly associated with the internal microscopic failure mechanism of DFC specimen, such as fiber fracture, matrix cracking, and fiber/matrix debonding. Fiber failures in the DFC specimens were distinguishable by showing the highest AE energy amplitude. They were dependant on the fiber diameters. Matrix cracking was determined from the relatively lower AE amplitude and AE energy, whereas fiber/matrix debonding could not be successfully isolated. AE method, however, can be applicable to the fragmentation method for interfacial strength(IFSS) in DFC specimens with adjusting the threshold to isolate fiber breaks from matrix crack and debonding.

• Journal of the Korean Ceramic Society
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• v.34 no.3
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• pp.303-313
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• 1997

To enhance the strength and formability of MCFC matrixes, alumina/${\gamma}$-LiAlO2 fiber-reinforced ${\gamma}$-LiAlO2 ma-trixes have been investigated. The MCFC matrixes with the thickness of 500~600 ${\mu}{\textrm}{m}$ were prepared by tape-casting of the slurry containing 10~30wt% fibers, followed by heat-treating up to $650^{\circ}C$. The porosity of fi-ber-reinforced matrixes decreased with the content of fibers, while the appropriate porosity(50~60%) for MCFC matrixes could be attained by adding larger ${\gamma}$-LiAlO2 particles with the diameter of about 50${\mu}{\textrm}{m}$ up to 50 wt%. The optimum length and content of the alumina fiber, both in the alignment of fibers and the enhancement of the strength, were found to be below 250${\mu}{\textrm}{m}$ and 20 wt%, respectively. On the other hand, the strength(156 gf/$\textrm{mm}^2$) of the ${\gamma}$-LiAlO2 matrix reinforced with ${\gamma}$-LiAlO2 fibers prepared in this study was improved by 20~40% in comparison with the alumina-fiber-reinforced matrix. It was also found that the alu-mina-fiber-reinforced matrix was completely corroded in molten carbonates but the ${\gamma}$-LiAlO2 was not.

• Journal of the Korean Ceramic Society
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• v.46 no.3
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• pp.301-305
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• 2009

The novel carbon coating process for interlayer of fiber reinforced ceramic composites between fiber and matrix was performed by carbonizing phenolic resin solution that coated on fiber surface in $N_2$ atmosphere at $600^{\circ}C$ to improve the strength and fracture toughness of CMC(ceramic matrix composite). 160 nm carbon layer was coated on fiber surface with 5 vol% of phenolic resin solution. Since the process temperature ($600^{\circ}C$) is lower than chemical vapor deposition($900{\sim}1000^{\circ}C$), the strength and toughness could be preserved. Furthermore the coating thickness uniformity was improved to 8% of deviation along the stacking sequence. Therefore, prevention from fiber degradation during coating process and controlling coating thickness uniformity along the preform depth were achieved by coating with phenolic resin carbonizing method.

• Structural Engineering and Mechanics
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• v.57 no.1
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• pp.105-126
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• 2016

In the present study, modelling and vibration control of axially moving laminated Carbon nanotubes/fiber/polymer composite (CNTFPC) plate under initial tension are investigated. Orthotropic visco-Pasternak foundation is developed to consider the influences of orthotropy angle, damping coefficient, normal and shear modulus. The governing equations of the laminated CNTFPC plates are derived based on new form of first-order shear deformation plate theory (FSDT) which is simpler than the conventional one due to reducing the number of unknowns and governing equations, and significantly, it does not require a shear correction factor. Halpin-Tsai model is utilized to evaluate the material properties of two-phase composite consist of uniformly distributed and randomly oriented CNTs through the epoxy resin matrix. Afterwards, the structural properties of CNT reinforced polymer matrix which is assumed as a new matrix and then reinforced with E-Glass fiber are calculated by fiber micromechanics approach. Employing Hamilton's principle, the equations of motion are obtained and solved by Hybrid analytical numerical method. Results indicate that the critical speed of moving laminated CNTFPC plate can be improved by adding appropriate values of CNTs. These findings can be used in design and manufacturing of marine vessels and aircrafts.

• Journal of Mechanical Science and Technology
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• v.16 no.2
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• pp.192-202
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• 2002

In particle or short-fiber reinforced composites, cracking of the reinforcements is a significant damage mode because the cracked reinforcements lose load carrying capacity. This paper deals with an incremental damage theory of particle or short-fiber reinforced composites. The composite undergoing damage process contains intact and broken reinforcements in a matrix. To describe the load carrying capacity of cracked reinforcement, the average stress of cracked ellipsoidal inhomogeneity in an infinite body as proposed in the previous paper is introduced. An incremental constitutive relation on particle or short-fiber reinforced composites including progressive cracking of the reinforcements is developed based on Eshelby's (1957) equivalent inclusion method and Mori and Tanaka\`s (1973) mean field concept. Influence of the cracking damage on the stress-strain response of composites is demonstrated.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.29-36
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• 2000

This investigation has been studied about friction and wear properties which were important problem, when carbon fiber reinforced plastic(CFRP) was used practically. Unidirection carbon fiber reinforced composites was fabricated with epoxy resin matrix and carbon fiber as a reinforced, and its surface was modified by the ion-assisted reaction. And then we tested the their friction and wear properties according to the ion-irradiation. when the amount of ion-irradiation was 1${\times}$10l6$\^$16/ ions/$\textrm{cm}^2$, the friction coefficient values were about 0.1, where as, the friction coefficient values of non-treatment composites were about 0.16. The former was the stablest in wear mode. We know that ion-irradiation was not proportioned to the friction coefficient, so we found the optimal conditions of the friction and wear according to the ion-irradiation.

• Carbon letters
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• v.9 no.4
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• pp.316-323
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• 2008

The factors that influence ablation resistance in fiber composites are properties of the reinforced fiber and matrix, plugging quantity of fiber, geometrical arrangement, crack, pore size, and their distributions. To examine ablation resistance according to distribution of crack and pore size that exist in carbon/carbon composites, this study produced various sizes of unit cells of preforms. They were densified using high pressure impregnation and carbonization process. Reinforced fiber is PAN based carbon fiber and composites were heat-treated up to $2800^{\circ}C$. The finally acquired density of carbon/carbon composites reached more than $1.932\;g/cm^3$. The ablation test was performed by a solid propellant rocket engine. The erosion rate of samples is below 0.0286 mm/s. In conclusion, in terms of ablation properties, the higher degree of graphitization is, the more fibers that are arranged vertically to the direction of combustion flame are, and the less interface between reinforced fiber bundle and matrix is, the better ablation resistance is shown.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.4
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• pp.1146-1153
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• 1996

The properties of FRP(fiber-reinforced plastics) depend not only on the characteristics of the matrix but also on the structure of fiber mat and the fiber type of reinforcement. Therefore it is very important to study the characteristics of reinforcement and matrix. In this paper, a method is proposed which can be used to measure the mean coeffcient of separation for the press molding of FRP, and the mean equivalent coefficient of separation is obtained from the separation coefficient. And the relationship between the mean equivalent coefficient of separation and the structure of fiber mat is discussed. The effects of corrlelation coefficient between separation and orientation on the mean equivalent coefficient are also presented.

• Korean Journal of Materials Research
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• v.31 no.11
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• pp.626-634
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• 2021

Cu matrix composites reinforced with chopped carbon fiber (CF), which is cost effective and can be well dispersed, are fabricated using electroless plating and hot pressing, and the effects of content and alignment of CF on the thermal properties of CF/Cu composites are studied. Thermal conductivity of CF/Cu composite increases with CF content in the in-plane direction, but it decreases above 10% CF; this is due to reduction of thermal diffusivity related with phonon scattering by agglomeration of CF. The coefficient of thermal expansion decreases in the in-plane direction and increases in the through-plane direction as the CF content increases. This is because the coefficient of thermal expansion of the long axis of CF is smaller than that of the Cu matrix, and the coefficient of thermal expansion of its short axis is larger than that of the Cu matrix. The thermal conductivity is greatly influenced by the agglomeration of CF in the CF/Cu composite, whereas the coefficient of thermal expansion is more influenced by the alignment of CF than the aggregation of CF.