• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.31-34
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• 2005

For the damage tolerance improvement of conventional laminated composites, stitching process has been utilized for providing through-thickness reinforcements. 2D prefonl1S were stacked with S-2 glass plain weave, and 3D preforms were fabricated using the stitching process. For the matrix system, epoxy and phenol resins were considered. To examine the damage resistance performance the low velocity drop weight impact test has been carried out, and the impact damage was examined by scanning image. CAI (Compressive After Ih1paet) tests were also conducted to evaluate residual compressive strength. Compared with 2D epoxy composites, 2D phenol composites showed drastic reduction in the compressive strength prior to impact because of the higher contents of voids. The damage area of 2D phenol composites were also larger than that of 2D epoxy composites. However, by introducing the stitching, the damage area of 3D phenol composites was reduced by 60%, while the CAI strength improvement was negligible.

• Composites Research
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• v.29 no.5
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• pp.269-275
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• 2016

Multiscale hybrid composites, which consist of polymeric resins, microscale fibers and nanoscale reinforcements, have drawn significant attention in the field of advanced, high-performance materials. Despite their advantages, multiscale hybrid composites show challenges associated with nanomaterial dispersion, viscosity, interfacial bonding and load transfer, and orientation control. In this paper, carbon nanotube(CNT)/carbon fiber(CF)/polycarbonate(PC) multiscale hybrid composite were fabricated by a solution process to overcome the difficulties associated with controlling the melt viscosity of thermoplastic resins. The dependence of CNT loading was studied by varying the method to add CNTs, i.e., impregnation of CF with CNT/PC/solvent solution and impregnation of CNT-coated CF with PC/solvent solution. In addition, hybrid composites were fabricated through surfactant-aided CNT dispersion followed by vacuum filtration. The morphologies of the surfaces of hybrid composites, as analyzed by scanning electron microscopy, revealed the quality of PC impregnation depends on the processing method. Dynamic mechanical analysis was performed to evaluate their mechanical performance. It was analyzed that if the position of the value of tan ${\delta}$ is closer to the ideal line, the adhesion between polymer and carbon fiber is stronger. The effect of mechanical interlocking has a great influence on the dynamic mechanical properties of the composites with CNT-coated CF, which indicates that coating CF with CNTs is a suitable method to fabricate CNT/CF/PC hybrid composites.

• Journal of Sensor Science and Technology
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• v.29 no.1
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• pp.45-50
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• 2020

Magnetoelectric (ME) composites were designed using the PMN-PZT single crystal and Ni foils; the properties and magnetic-field sensitivities of ME composites with different piezoelectric vibration modes (i.e., 31, 32, and 36 modes that depend on the crystal orientation of the single crystal) were compared. In the off-resonance condition, the ME coupling properties of the ME composites with the 32 and 36 piezoelectric vibration modes were better than those of the ME composites with the 31 piezoelectric vibration mode. However, in the resonance condition, the ME coupling properties of the ME composites were almost similar, irrespective of the piezoelectric vibration mode. Additionally, in the off-resonance condition (at 1 kHz), the magnetic-field sensitivity of the ME composites with the 36 piezoelectric vibration mode was up to 2 nT and those of the ME composites with the 31 and 32 piezoelectric vibration modes were up to 5 nT. These magnetic-field sensitivities are similar to those offered by conventional high-sensitivity magnetic-field sensors; the potential of the proposed sensor to replace costly and bulky high-sensitivity magnetic field sensors is significant.

• Journal of the Korea Institute of Building Construction
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• v.4 no.3
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• pp.93-100
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• 2004

In recent years, it has widely been studied on the light-weight composites for the purpose of the large space and thermal insulation of building structures. The purpose of this study is to evaluate the properties of light-weight composites made by binders as cement, resin and polymer cement slurry. The concrete composites are prepared with various conditions such as polymer-cement ratio, void-filling ratio, type of resin, filler content and light-weight aggregate content, tested for thermal conductivity. From the test results, the thermal conductivity of concrete composites with the binder of cement tends to decrease with increasing polymer-cement ratio, and to increase with increasing void-filling ratio. The thermal conductivity of concrete composites with the binder of resin are markedly affected by the light-weight aggregate content, type of resin and filler content. The composites made by polymer-modified concrete and polymer cement slurry have a good thermal insulation property. From the this study, we can recommend the proper mix proportions for thermal insulation Panel or concrete. Expecially. the thermal conductivity of concrete composites made by polyurethane resin is almost the same as that of the conventional expanded polystyrene resin.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.3 s.258
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• pp.295-303
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• 2007

Degradation behaviors of filament-winded composites have been evaluated under the accelerated environmental test of high temperature, water immersion and thermal impact conditions. Two kinds of laminated composites coated by an urethane resin have been used: carbon-fiber reinforced epoxy(T700/Epon-826, CFRP) and glass-fiber reinforced phenolic (E-glass/phenolic, GFRP). For tensile strength of $0^{\circ}$ composites, CFRP showed little degradation while GFRP did high reduction by 25% under the influence of high temperature and water However for water-immersed $90^{\circ}$ composites tensile strength of both CFRP and GFRP showed high reduction. Bending strength and modulus of $90^{\circ}$ composites were largely reduced in water-immersion as well as high temperature environment. Urethane coating on the composite surface improved the bending properties by 20%, however hardly showed such improvement for water-immersed $90^{\circ}$ composites. In case of shear strength and modulus, both CFRP and GFRP showed high reduction by water-Immersion test but did a slight increase by high temperature and thermal impact conditions.

• Macromolecular Research
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• v.14 no.4
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• pp.456-460
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• 2006

The electrical, morphological, and mechanical properties of poly carbonate (PC)/multi-walled carbon nan-otube (MWNT) composites were studied by electrical conductivity, electromagnetic interference shielding efficiency (EMI SE), scanning electron microscopy, and tensile strength measurements. In the electrical property analysis of the PC/MWNT composites, the percolation threshold of the PC/MWNT composites was observed between 1.5 and 2.5 wt% MWNT content. From the electrical conductivity and EMI SE studies, the theoretical values of the EMI SE were in good agreement with the experimental values of the EMI SE. From the morphology of the PC/MWNT composites, it was observed that MWNT is dispersed homogenously in the PC matrix. From the electrical conductivity and morphological studies, it was suggested that the percolation threshold of the PC/MWNT composites is related with the morphological results in that MWNT is apparently interconnected to form an electrical pathway. The mechanical properties of the PC/MWNT composites peaked at the MWNT content of 2.5 wt%.

• Journal of Korea Foundry Society
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• v.13 no.6
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• pp.547-554
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• 1993

Aluminum alloy matrix composites reinforced with various amounts of $Al_2O_3$ short fibers have been produced by rheo-compocasting accompanied by hot pressing. When composites reinforced with fibers are produced by rheo-compocasting, S-L process is the most effective method for homogeneous dispersion of fibers. A sound composites with the improved orientation(3 dimension${\rightarrow}$2 dimension) of the fibers and increased volume fraction of them have been fabricated through the hot pressing of the casted composites. Fibers are broken down when rheo-compocasting, hot pressing, and $T_6$ treating. Among them fibers are broken down most heavily in the hot pressing. And even in the case of the composite reinforced with 30 vol% fibers, which showed the hardest fiber break down, aspect ratio(11.6) is higher than critical aspect ratio(10.7). The fiber strengthening effect in the composites has showed upto 573K. As the test temperature increases to the range of 573K, the effect has been higher. The fracture of composites is controlled by fiber from room temperature to 473K, but the fracture of composites is controlled by interface between fiber and matrix alloy above 473K.

• Journal of the Korean Ceramic Society
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• v.45 no.11
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• pp.667-674
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• 2008

In this study, we prepared Fe-activated carbon fiber(ACF)/$TiO_2$ composites with titanium (VI) n-butoxide (TNB) as the titanium source for ACF pre-treated with iron compounds through the impregnation method. In terms of textural surface properties, the composites demonstrate a slight decrease in the BET surface area of the samples and an increase in the amount of iron compounds treated. The surface morphology of the Fe-ACF/$TiO_2$ composites was characterized by means of SEM. The composites have a porous texture with homogenous compositions of Fe and titanium dioxide distributed on the sample surfaces. The phase formation and structural transition of the iron compounds and titanium dioxide were observed in X-ray diffraction patterns of the Fe-ACF/$TiO_2$ composites. The chemical composition of the Fe-ACF/$TiO_2$ composites, which was investigated with EDX shows strong peaks for the C, O, Fe and Ti elements. The photo degradation results confirm that the Fe-ACF/$TiO_2$ composites show excellent removal activity for the COD in piggery waste due to photocatalysis of the supported $TiO_2$, radical reaction by Fe species, and the adsorptivity and absorptivity of ACF.

• Transactions of Materials Processing
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• v.3 no.4
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• pp.427-439
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• 1994

The high temperature deformation behavior of $SiC_p/Al-Si$ composites and Al-Si matrix was studied by hot torsion test in a range of temperature from $270^{\circ}C$ to $520^{\circ}C$ and at strain rate range of $1.2{\times}10_{-3}~2.16{\times}10_{-1}/sec$. The hot restoration mechanisms for both matrix and composites were found to be dynamic recrystallization(DRX) from the investigation of flow curves and microstructural evolutions. The Si precipitates and SiC particles promoted DRX, and the peak strain$({\varepsilon}_p)$ of the composites was smaller than that of the matrix. Flow stresses of $SiC_p/Al-Si$ composites were found to be generally higher than the matrix, but the difference was quite small at higher temperature due to the decrease of capability of load transfer by SiC particles. With increasing temperature, failure strain of matrix and composites are inclined to increase, the increasing value of failure strain for the $SiC_p/Al-Si$ composites was small compared to that of matrix. The stress dependence of both materials on strain rate() and temperature(T) was examined by hyperbolic sine law, $\.{\varepsilon}=A_1[sinh({\alpha}{\cdot}{\sigma})]_n$exp(-Q/RT)

• Journal of Ocean Engineering and Technology
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• v.14 no.4
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• pp.49-55
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• 2000

This study has been investigated to apply fiber reinforced composites instead of asbestos as a friction material. the reinforced used was E-glass fiber and binder resin was phenol having good mechanical properties and heat resistance. And it has been also investigated the effect of molding conditions and some additives such and carbon black, alumina and rubber powder in E-glass fiber/phenol resin composite on the friction on the friction and wear characteristics. As a result, it was found that the molding conditions of E-glass fiber/phenol resin composites for friction materials had to be different from those of phenol resin and was found that the wear rate of E-glass fiber/phenol resin composites added alumina powder was higher than of composites added carbon black in the same wear distance. And it was found that friction coefficient of E-glass/phenol resin composites added carbon black was decreased and that of the composites added the powder of natural rubber and ABS rubber were increased compared to the composites.