• International Journal of Ocean System Engineering
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• v.3 no.3
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• pp.142-146
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• 2013

In this study, the effect of Carbon/PEEK composites on the tribological properties has been investigated. Also, its validity has been tested in the capacity of alternative materials of the Ti-based materials used for artificial hip joint. Moreover, this work evaluated the mechanical properties according to the fiber ply orientation, along with the fractured surfaces of the carbon/PEEK composites. The composites with a unidirectional orientation had higher tribological properties than those with a multidirectional orientation. This was caused by the debonding between the carbon fiber and the PEEK, which was proportional to the contact area between the sliding surface and the carbon fiber. The friction test results showed that there were no significant differences in relation to the fiber ply orientation. However, the friction properties of the carbon/PEEK composites were higher than those of the carbon/epoxy composites. In addition, the results showed that a composite that slid in a direction normal to the prepreg lay-up direction had a smaller friction coefficient than one that slid in a direction parallel to the prepreg lay-up direction.

• Polymer(Korea)
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• v.24 no.5
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• pp.721-727
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• 2000

The electrolytic plating of a metallic nickel on carbon fiber surfaces was carried out to improve mechanical interfacial properties of carbon fiber/epoxy resin composites. The surface characteristics of carbon fibers and the mechanical interfacial properties of final composites were characterized by X-ray photoelectron spectroscopy (XPS) and interlaminar shear strength (ILSS), respectively. It was found that the electrolytic Ni-plating conditions significantly affected the degree of adhesion at interfaces between carbon fibers and epoxy resin matrix in a composite system. Especially, the increase of O,$_{1s}$/$C_{1s}$ ratio, production of NiO groups, and formation of metallic nickel on the nickel-plated carbon fiber surfaces led to an increase of the ILSS of the composites. Also, the ILSS of the composites was greatly correlated with the $O_{1s}$/$C_{1s}$ ratio of the carbon fibers treated in this work.is work.

• Steel and Composite Structures
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• v.17 no.6
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• pp.825-834
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• 2014

This manuscript presents an experimental investigation on the effect of Multi-walled carbon nanotubes (MWCNTs) addition on the tensile, flexural and impact properties of woven Kevlar fabric reinforced epoxy composites. MWCNTs were dispersed in the epoxy resin by sonication technique and the samples were fabricated by hand layup laminating procedure. Scanning electron microscopy (SEM) was used to characterize the microstructure of produced samples. The effects of adding small amounts (${\leq}1%$) of MWCNT on the tensile, flexural and impact (Izod) behaviors of laminated composites were analyzed. Results revealed that MWCNTs enhanced the Young's modulus up to 20%, bending modulus up to 40%, and impact strength up to 45% in comparison with woven Kevlar fabric/epoxy composites. It was found that the maximum improvements in mechanical properties were happened for 0.5 wt.% MWCNT.

• Composites Research
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• v.27 no.4
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• pp.168-173
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• 2014

The optimum condition of glass fiber/epoxy composites was investigated according to mixing ratio of two epoxy matrices. Novolac type epoxy and isocyanate modified epoxy were used as composites matrix. Based on chemical composition of mixing matrix, optimum mixing ratio of epoxy resins was obtained through various experiments. In order to investigate thermal stability and interface of epoxy resin, glass transition temperature was observed by DSC instrument, and static contact angle was measured by reflecting microscope. Change of IR peak and $T_g$ was conformed according to different epoxy mixing ratio. After fabrication of glass fiber/epoxy composites, tensile, compression, and flexural properties were tested by UTM by room and high temperature. The composites exhibited best mechanical properties when epoxy mixing ratio was 1:1.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.42-45
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• 2003

Nondestructive damage sensing and mechanical properties for acid-treated carbon nanotube (CNT) and nanofiber (CNF)/epoxy composites were investigated using electro-micromechanical technique and acoustic emission (AE). Carbon black (CB) was used to compare to CNT and CNF. The results were compared to the untreated case. The fracture of carbon fiber was detected by nondestructive acoustic emission (AE) relating to electrical resistivity under 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. Reinforcing effect of CNT obtained from apparent modulus measurement was the highest in the same content. For surface treatment case, the damage sensitivity and reinforcing effect were higher than those of the untreated case. 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.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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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.

• Applied Chemistry for Engineering
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• v.27 no.3
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• pp.285-290
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• 2016

To improve properties of epoxy composites, surfaces of the illite and carbon nanotube (CNT) were treated by fluorine gas. The fluorinated illite and CNT were then characterized by X-ray photoelectron microscopy (XPS) and the mechanical and thermal properties of their composites were evaluated. The tensile and impact strengths and thermal stability of the composites increased upto about 59%, 18% and 124%, respectively compared to those of the neat epoxy. Improvements of mechanical and thermal properties in the composites were attributed that the fluorination of illite and carbon nanotube helps to enhance the dispersion in epoxy resin and interfacial interaction between them.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.5
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• pp.411-422
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• 2010

Self-sensing on micro-failure, dispersion degree and relating properties, of carbon nanotube(CNT)/epoxy composites, were investigated using wettability, electro-micromechanical technique with acoustic emission(AE). Specimens were prepared from neat epoxy as well as composites with untreated and acid-treated CNT. Degree of dispersion was evaluated comparatively by measuring volumetric electrical resistivity and its standard deviation. Apparent modulus containing the stress transfer was higher for acid-treated CNT composite than for the untreated case. Applied cyclic loading responded well for a single carbon fiber/CNT-epoxy composite by the change in contact resistivity. The interfacial shear strength between a single carbon fiber and CNT-epoxy, determined in a fiber pullout test, was lower than that between a single carbon fiber and neat epoxy. Regarding on micro-damage sensing using electrical resistivity measurement with AE, the stepwise increment in electrical resistivity was observed for a single carbon fiber/CNT -epoxy composite. On the other hand, electrical resistivity increased infinitely right after the first carbon fiber breaks for a single carbon fiber/neat epoxy composite. The occurrence of AE events of added CNT composites was much higher than the neat epoxy case, due to micro failure at the interfaces by added CNTs.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.199-202
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• 2002

Interfacial properties and electrical sensing for fiber fracture in carbon and SiC fibers/epoxy composites were investigated by the electrical resistance measurement and fragmentation test. As fiber-embedded angle increased, interfacial shear strength (IFSS) of two-type fiber composites decreased, and the elapsed time was long to the infinity in electrical resistivity. The initial slope of electrical resistivity increased rapidly to the infinity at higher angle, whereas electrical resistivity increased gradually at small angle. Furthermore, both fiber composites with small embedded angle showed a fully-developed stress whitening pattern, whereas both composites with higher embedded angle exhibited a less developed stress whitening pattern. As embedded angle decreased, the gap between the fragments increased and the debonded length was wider for both fiber composites. Electro-micromechanical technique can be a feasible nondestructive evaluation to measure interfacial sensing properties depending on the fiber-embedded angle in conductive fiber reinforced composites.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.155-160
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• 2004

This paper presents a study on the permittivities of the carbon black/epoxy composite at microwave frequency. The measurements were performed at the frequency band of $1 GHz\~18GHz$. The results show that the complex permittivities of composites depend strongly on the natures and concentrations of the carbon black dispersion. The frequency spectrums of dielectric constants and ac conductivities of composites show the good conformities with descriptions of the percolation theory. The carbon black concentration dependencies do not have conformities with the descriptions of percolation theory and there is no peculiar concentration like percolation threshold, on that concentration, the conductivity of composite jumps up. A new scheme, that is a branch of Lichtenecker-Rother formula, is proposed to obtain a mixing law to describe the complex permittivities of the composites as function frequency and concentration of carbon black.