• Korean Journal of Materials Research
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• v.3 no.3
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• pp.292-299
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• 1993

In this paper the effects of the length of carbon fiber on the wear properties of carboni carbon composites were investigated. Carbon/carbon composites were fabricated by the liquid impregnation method using the resol-type phenolic resin as a matrix precursor and PAN-based, non-surface treated carbon fiber as a reinforcement. The measured values of the friction coefficient of carbon/carbon composites against AlSl 304 stainless steel ranged from 0.2 to 0.3 under the operating condition used in this study. The effect of the length of carbon fiber on the friction coefficient of carbon/carbon composites were not found. But, it was realized that the wear rate of carbon/carbon composites tends to increase, as the length of carbon fiber increases.

• Journal of the Korean Ceramic Society
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• v.34 no.5
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• pp.483-490
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• 1997

Al2O3/metal composites were fabricated by oxidation and reaction of molten Al-alloy into two types of commercial Al2O3-SiO2 fibrous insulation board. The growth rate, composition and microstructure of these materials were described. An AlZnMg(7075) alloy was selected as a parent alloy. Mixed polycrystalline fiber and glass phase fiber were used as a filler. The growth surface of an alloy was covered with and without SiO2. SiO2 powder was employed as a surface dopant to aid initial oxidation of Al-alloy. Al-alloy, SiO2, fiber block and growth inhibitor CaSiO3 were packed sequentially in a alumina crucible and oxidized in air at temperature range 90$0^{\circ}C$ to 120$0^{\circ}C$. The growth rate of composite layer was calculated by measuring the mass increasement(g) per unit surface($\textrm{cm}^2$). XRD and optical microscope were used to investigate the composition and phase of composites. The composite grown at 120$0^{\circ}C$ and with SiO2 dopant showed rapid growth rate. The growth behavior differed a little depending on the types of fiber used. The composites consist of $\alpha$-Al2O3, Al, Si and pore. The composite grown at 100$0^{\circ}C$ exhibited better microstructure compared to that grown at 120$0^{\circ}C$.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.6
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• pp.1422-1430
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• 1995

Al6061 alloy reinforced with 15 volume% of Saffil fibers was fabricated by squeeze infiltration method. Uniform distribution of reinforcements and good bondings between reinforcements and matrix alloy were found in the microstructure of composites. Comparing with A16061 matrix alloy, tensile strength and elastic modulus of $Al_{2}$O$_{3}$/Al composites were increased up to 26% and 31%, respectively. Cyclic deformation and fatigue behavior of $Al_{2}$O$_{3}$/Al metal matrix composites were studied. The specimens were cycled using tension-tension(R=0.1) loading and under load controlled fatigue test. Cyclic stress-displacement curve through fatigue test was obtained. Fatigue strength of $Al_{2}$O$_{3}$/Al composites was about 200 MPa, i.e.0.55 of applied stress level(q). During fatigue test, $Al_{2}$O$_{3}$/Al composites displayed cyclic hardening at all applied stress levels. The most of resultant displacement due to permanent plastic deformation occurred in less than the first 5% of fatigue life. Displacement-to-failure of the fatigue test was smaller than that of the tensile test because of accumulative damage by cumulative plastic deformation.

• Journal of the Korean Ceramic Society
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• v.34 no.5
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• pp.500-504
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• 1997

Perovskite Pb0.7Ba0.3Zn1/3Nb2/3O3 substituted with 0.3 mole fraction for Pb-site in PbZn1/3Nb2/3O3 relaxor and pyrochlore Pb1.83Ba0.29Zn1.71Nb2/3O6.39 were mixed and dielectric characteristics of this composites were investigated. Percolation limit of perovskite phase, which was determined by microstructural observation in the composite as an isolation of perovskite phase from pyrochlore matrix, was 28.9-47.5 vol%. Ferroelectric phase transition below percolation limit depends on a parameter which affects the propagation of lattice vibration between isolated perovskite phase and pyrochlore matrix. Therefore, it is believed that ferroelectric lattice vibration of isolated perovskite phase could be transfered to pyrochlore matrix when the oxygen octahedra are linked in 3-dimension and highly polarizable Pb2+ ions are contained in both phases.

• Journal of Adhesion and Interface
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• v.9 no.3
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• pp.27-33
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• 2008

A series of aluminum acetylacetonate (AlACA) belonging in inorganic chelate calculating with the ratio of -COOH mole in PSA (0, 0.25, 0.5, 0.75, 1) and a series of PSA with different acrylic acid contents (3 wt%, 7 wt%, 10 wt%) were blended and measured gel contents, probe tack, peel strength, SAFT. With the increasing of aluminum acetylacetonate contents, the network structure was formed and gel contents were increased. Probe tack fibrillation and peel strength were decreased following the addition of aluminum acetylacetonate. SAFT were significantly changed with the change of acrylic acid contents in PSA. From these results, aluminum acetylacetonate could be used in the range of which would not change the performance a lot, and cure the PSA.

• Composites Research
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• v.28 no.3
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• pp.124-129
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• 2015

CNT and GNP have several excellent mechanical properties including, high strength, Young's modulus, thermal conductivity, corrosion resistance, electronic shielding and so on. In this study, CF/CNT, GNP/epoxy composites were manufactured by varying the CNT weight ratio at 2wt% and 3wt%, GNP weight ratio at 0.5wt% and 1 wt%. The composites were manufactured by mechanical method (3-roll-mill). Tensile, impact and wear tests were performed according to ASTM standards D638, D256 and D3181 respectively. The results showed that, CF/GNP0.5 wt%/epoxy composites gave good mechanical property in all composites, e.g., tensile strength, impact and were resistance.

• Journal of the Korean Ceramic Society
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• v.55 no.6
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• pp.556-561
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• 2018

In this study, we performed a microwave sintering (MWS) of $Al_2O_3$ ceramic and $Al_2O_3$-based composites with nominal contents of graphene nanoplatelets (GPLs) of 0.2, 0.4, 0.6, and 0.8 vol%. The GPL dispersion in N-methyl pyrroleketone was optimized to deagglomerate the GPLs without damaging their structure. Dense composites were then obtained by MWS at $1500^{\circ}C$ for 30 min. The effects of different GPL contents on the phase compositions, microstructures, and mechanical properties of the composites were investigated. The microstructures of the composites became finer with the incorporation of the GPLs. The well-dispersed GPL fillers led to higher sintered densities in the composites. The optimal mechanical properties were achieved with 0.4 vol% GPLs. For this sample, the hardness, fracture toughness, and bending strength were $2000kgf/mm^2$, $6.19MPa{\cdot}m^{1/2}$, and 365.10 MPa, respectively. The addition of GPL could improve the microstructure of the $Al_2O_3$ ceramic and has potential to improve the fracture toughness of the ceramics.

• Journal of the Korean Magnetics Society
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• v.4 no.3
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• pp.208-213
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• 1994

Wide-band absorbency and small layer thickness are required in the high- performance microwave absorber. In order to reduce the thickness of the absorber, ferrite-iron-rubber composites were proposed and its properties were investigated. The increase in both real part of perrreability and permittivity of the composites were observed with addition of -Fe powder and this behavior results in the decrease of fm dm term. The matching thicknesses of ferrite-iron-ruber composites were relatively small(0.5~2.0 mm) in the frequency range of 3~17 GHz as comIBfed to than that of ferrite-rubbr composit.

• Transactions of Materials Processing
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• v.25 no.6
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• pp.402-408
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• 2016

A manufacturing technology of carbon fiber composites with thermoplastic polymer pellets and continuous woven fiber was investigated using a compression molding process. To secure the impregnation of resin into the porosity of fabric the composite specimens were prepared with general injection-molding grade polypropylene pellets and low viscosity polycarbonate pellets. Tensile tests of polypropylene and polycarbonate composites were performed. Polycarbonate composites showed higher fracture strength than that of polypropylene composites because of the difference of matrix properties. However, the increase rate of strength was lower than that of polypropylene composites due to the difference of coherence between matrix and reinforcement. To investigate the effect of carbon fiber volume fraction on the fracture strength variation polypropylene composites with different volume fraction were compression molded and tensile tests were performed together. It was shown that the fracture strength of the polypropylene composites increased by 3.2, 5.4 and 6.9 times with the increase of carbon fabric volume fraction of 0.256, 0.367, and 0.480, respectively.

• Korean Journal of Materials Research
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• v.9 no.2
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• pp.132-138
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• 1999

In order to investigate the toughening characteristic by microcrack formation in ceramic composites, $Al_2$O$_3$/(0~20)vol% YAG composites containing equiaxed second grains were fabricated using$ Al_2$$O_3$ during hot-pressing. AE(acoustic emission) measurements have been coupled with fracture toughness experiments of SENB method, to evaluate the microcrack formation and the improvement in fracture toughness of ceramic composites. Formation of microcrack was detected by Ae. The generation of AE events increased with increasing of load when load was applied at specimen. The AE events are generated mainly around at maximum load. Specially, the detected AE evetns of composites are many as compared with monolithic $Al_2$$O_3$. Fracture toughness of composites was improved than that of monolithic alumina. $Al_2$O$_3$/YAG composites exhibit main toughening effects by microcracking, results from mutual coalesence of microcracks being generated under applied load. However, there are few toughening mechanism like microcracking in monolithic alumina.