• Journal of Powder Materials
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• v.20 no.1
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• pp.33-36
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• 2013

A bulk metallic glass-forming alloy, $Ni_{59}Zr_{20}Ti_{16}Si_2Sn_3$ metallic glass powders was used for good commercial availability and good formability in supercooled liquid region. In this study, the Ni-based metallic glass was synthesized using by high pressure gas atomized metallic glass powders. In order to create a bulk metallic glass sample, the $Ni_{59}Zr_{20}Ti_{16}Si_2Sn_3$ metallic glass powders with ball-milled Ni-based amorphous powder with 40%vol brass powder and Cu powder for 20 hours. The composite specimens were prepared by Spark Plasma Sintering for the precursor. The SPS was performed at supercooled liquid region of Ni-based metallic glass. The amorphous structure of the final sample was characterized by SEM, X-ray diffraction and DSC analysis.

• Journal of the Korean Ceramic Society
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• v.46 no.3
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• pp.323-329
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• 2009

Influences of ceramic filler types and dose on the sintering, phase evolution, and dielectric properties of ceramic/CaO-$Al_2O_3-SiO_2$ glass composites were investigated. All of the specimens were sintered at $900^{\circ}C$ for 2 h, which conditions are required by the lowtemperature co-firing ceramic (LTCC) technology. Ceramic fillers of $Al_2O_3,\;SiO_2$, kaolin, and wollastonite were used. The addition of $Al_2O_3$ filler yielded the crystalline phases of alumina and wollastonite, and the densification over 95% of the relative density was achieved up to 50 wt% addition of the filler. For the cases of the fillers of $SiO_2$, kaolin, and wollastonite, crystalline phases of quartz, mullite, and wollastonite formed, while the densification decreased monotonically with the filler addition. In overall, all the investigated fillers with 10 wt% addition resulted in a reasonable sintering (over 95 %) and low dielectric constants (less than 6), demonstrating the feasibility of the investigated composites for application to a LTCC substrate material with a low dielectric constant.

• Composites Research
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• v.26 no.4
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• pp.245-253
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• 2013

In this paper, we developed a theoretical model which is able to predict the tensile strength and elastic modulus of hybrid composites reinforced by two types of randomly distributed discontinuous reinforcements. For this, we considered two known models; One is a prediction model based on the assumption that the composite is reinforced by two types of well aligned continuous reinforcements. The other is a statistical model for the composite which is reinforced by only one type of randomly distributed discontinuous reinforcements. In order to evaluate the validity of accuracy of our prediction model, we measured the strength and elastic modulus of polypropylene hybrid composite reinforced by talc and short glass fiber. We found that the present model drastically enhances the accuracy of strength prediction compared to an existing model, and predicts the elastic modulus within the same order with experimentally measured values.

• Steel and Composite Structures
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• v.36 no.4
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• pp.417-426
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• 2020

Drilling processes in fiber-reinforced polymer composites are essential for the assembly and fabrication of composite structural parts. The economic impact of rejecting the drilled part is significant considering the associated loss when it reaches the assembly stage. Therefore, this article tends to illustrate the effect of cutting conditions (feed and speed), and laminate thickness on thrust force, torque, and delamination in drilling woven E-glass fiber reinforced epoxy (GFRE) composites. Four feeds (0.025, 0.05, 0.1, and 0.2 mm/r) and three speeds (400, 800, and 1600 RPM) are exploited to drill square specimens of 36.6×36.6 mm, by using CNC machine model "Deckel Maho DMG DMC 1035 V, ecoline". The composite laminates with thicknesses of 2.6 mm, 5.3 mm, and 7.7 mm are constructed respectively from 8, 16, and 24 glass fiber layers with a fiber volume fraction of about 40%. The drilled specimen is scanned using a high-resolution flatbed color scanner, then, the image is analyzed using CorelDraw software to evaluate the delamination factor. Multi-variable regression analysis is performed to present the significant coefficients and contribution of each variable on the thrust force and delamination. Results illustrate that the drilling parameters and laminate thickness have significant effects on thrust force, torque, and delamination factor.

• Tribology and Lubricants
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• v.36 no.3
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• pp.133-138
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• 2020

In this paper, we present an experimental investigation of the friction coefficient and wear area change of carbon/epoxy and E-glass/epoxy composites depending on the fiber direction (0°/90°). We compared the results of the case where the sliding direction is parallel to the fiber direction (0°) with that of the case where it is perpendicular to the fiber direction (90°). The ball-on-plate wear test equipment was used to cause wear in both directions. Two types of specimens were prepared with thicknesses of 3 mm-one made of carbon fiber reinforced plastic composite (CFRP) and the other of glass fiber reinforced plastic composite (GFRP). A normal force of 20 N was applied to the specimen and the sliding speed was 10 mm/s and the sliding distance was set to 20 m to perform the wear test. The CFRP demonstrates superior tribological characteristics compared to the GFRP. This outcome is attributed to graphitization of carbon, which serves as solid lubricating particles. In addition, both CFRP and GFRP are worn more in the 90° direction than in the 0° direction. This is due to the greater occurrence of fiber breakage and separation in the 90° direction than in the 0° direction. This study is expected to be utilized as basic data for understanding the friction and wear characteristics of CFRP and GFRP composites along the fiber direction and to apply the appropriate material.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.3
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• pp.211-217
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• 2012

In this paper, experimental tests and theoretical studies were carried out to evaluate the tensile behavior of the sprayed FRP composite with chopped glass fiber. For this, a series of tensile strength tests with various strain rates were conducted on the specimens of the matrix and sprayed FRP composite. Sprayed FRP composite contained chopped glass fibers with fiber length of 15mm and a specific volume fraction of fibers of 25 %. An inverse simulation was conducted to simulate the strain rate sensitivity based on the present experimental data of the epoxy resin. The simulated viscosity value is adapted to the micromechanics-based viscoelastic damage model(Yang et al., 2012), and the overall tensile behavior of sprayed FRP composites is predicted. It was seen from the comparative study between present experimental data and predication results that the proposed methodology can be used to predict the viscoelastic behavior of the sprayed FRP composite.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.5
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• pp.397-404
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• 2009

Effects of ceramic filler types and dose on the low temperature sintering and dielectric properties of ceramic/$CaO-Al_2O_3-SiO_2$ (CAS) glass composites were investigated. All of the specimens were sintered at $850{\sim}900^{\circ}C$ for 2 h, which conditions are required by the low-temperature co-firing ceramic (LTCC) technology. Ceramic fillers of $CaCO_3$, $Al_2O_3$, $CaCO_3-Al_2O_3$ mixture, and $CaCO_3-Al_2O_3$ compound ($CaAl_2O_4$), respectively, were used. The addition of $Al_2O_3$ yielded the crystalline phase of alumina, which was associated with the inhibition of sintering, while, $CaCO_3$ resulted in no apparent crystalline phase but the swelling was significant. The additions of $CaCO_3-Al_2O_3$ mixture and $CaAl_2O_4$, respectively, yielded the crystalline phases of alumina and anorthite, and the sintering properties of both composites increased with the increase of filler addition and the sintering temperature. In addition, the $CaAl_2O_4$/CAS glass composite, sintered at $900^{\circ}C$, demonstrated good microwave dielectric properties. In overall, all the investigated fillers of 10 wt% addition, except $CaCO_3$, yielded reasonable sintering (relative density, over 93 %) and low dielectric constant (less than 5.5), demonstrating the feasibility of the investigated composites for the application of the LTCC substrate materials.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2661-2665
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• 2011

In order to evaluate the structural integrity of a GFRP composite bogie frame due to flying railway ballast, the low velocity impact test and compressive test after impact was conducted for glass fiber/epoxy 4-harness satin woven laminate composites applied to skin part of a bogie frame. The impact test was performed using a instrumented impact testing system with energy levels of 5J, 10J and 20J and the designed impactor based on typical railway ballast shapes such as sphere, cube and cone to simulate the ballasted track environments. The compressive strength was tested to according to ASTM D7137 to evaluate the degradation of mechanical property of impact damaged laminate composites. The results showed that the damage area and the degradation of compressive strength after impact for laminate composites was increased with increase in impact energy for all ballast shapes and was particularly most influenced by cone ballast shape.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.195-198
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• 2005

The role of elastic/plastic mismatch on the contact crack initiation is investigated for designing desirable surface-coated asymmetric layered composites. Various layered composites such as $Si_3N_4$ ceramics on $Si_3N_4+BN$ composite, soda-lime glass on various substrates with different elastic modulus for the analysis. Spherical indentation is conducted for producing contact cracks from the surface or interface between the coating and the substrate layer. A finite element analysis of the stress fields in the loaded layer composites enables a direct correlation between the damage patterns and the stress distributions. Implications of these conclusions concerning the design of asymmetric layered composites indicate that the elastic modulus mismatch is one of the important parameter for designing layered composite to prevent the initiation of contact cracks.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.44 no.3
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• pp.250-256
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• 2008

Generally the side plate materials of FRP ship are composed of glass fiber and unsaturated polyester resin composites(GFRP composites). In this study, the effect of applied load and sliding speed on friction and wear characteristics of these materials were investigated at ambient temperature by pin-on-disc friction test. The cumulative wear volume, friction coefficient and wear rate of these materials for SiC abrasive paper were determined experimentally. The cumulative wear volume showed a tendency to increase nonlinearly with increase of sliding distance and was dependent on applied load and sliding speed for these composites. The friction coefficient of GFRP composites was increased as applied load increased at same sliding speed in wear test. It was verified by SEM photograph of worn surface that major failure mechanisms were microfracture, deformation of resin, cutting and cracking.