• Journal of the Korean Society of Safety
• /
• v.19 no.4 s.68
• /
• pp.31-35
• /
• 2004

The A17075/CFRP multi-layered hybrid laminate material consists of the alternating A17075-T6 sheets and carbon/epoxy prepregs of M40 fade. The influence of volume fraction and fiber orientation of A17075/CFRP layer on flexural properties of A17075/CFRP laminate alternating A17075-T6 and carbon/epoxy prepreg was investigated. The results obtained from the experimental analysis are as follows: 1. In the $0^{\circ}$ fiber orientation, the mont of increase of the flexural rigidity was $20.5\%$ at the $26.5\%$ volume fraction and $38.0\%\;at\;the\;35.7\%$ volume fraction compared with the flexural rigidity level(20.0GPa) of the $10\%$ volume fraction of CFRP. 2. In the $\pm45^{\circ}$ fiber orientation the amount of decrease of the flexural rigidity was $23.5\%\;at\;the\;20.0\%$ volume fraction and $31.5\%\;at\;the\;33.3\%$ volume fraction compared with the flexural rigidity level of the $10\%$ volume fraction of CFRP. 3. In the $0^{\circ}$ fiber orientation, the flexural strength was 481.5MPa at the $10\%$ volume fraction of CFRP and 583.8MPa at the $26.5\%$ volume fraction and 653.7MPa at the $35.7\%$ volume faction. 4. In the $\pm45^{\circ}$ fiber orientation, the flexural strength was 354.0MPa at the $20.0\%$ volume fraction of CFRP and 340.5MPa at the $33.3\%$ volume fraction.

• Journal of the Korea Concrete Institute
• /
• v.28 no.2
• /
• pp.213-221
• /
• 2016

Uniaxial compression tests for ultra-high performance hybrid steel fiber reinforced concrete (UHPC) were performed to evaluate the compressive behavior of UHPC. The UHPC for testing contains hybrid steel fibers with a predetermined ratio using a length of 19 mm and 16 mm straight typed steel fibers. Test parameter was determined as a fiber volume ratio to investigate the effect of fiber volume ratio on the strength and secant modulus of elasticity. Test results showed that the compressive strength and elastic modulus of UHPC increased with increasing the fiber volume ratio. Based on the test results, the compressive strength and modulus of elasticity equations were proposed as function of the compressive strength of unreinforced and fiber reinforced UHPC, respectively. The simplified equations for predicting the mechanical properties of the UHPC were a good agreement with the test data. The proposed equations are expected to be applied to the SFRC and UHPC with steel fibers.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.20 no.4
• /
• pp.237-242
• /
• 2000

This study was conducted to investigate the effects of cutting frequency on dry matter yield and nutritive value between heading and headless varieties of sorghumxsudangrass hybrid in 1998. Treatments were var. TE hay grazer(heading type) and Jumbo(headless type) as main plot, and 1, 2, and 3 cutting times per a year as sub plot. Although plant height of sorghumxsudangrass hybrid was no significant difference among treatments, headless type was very slightly higher than that of heading type, and both of variety decreased with 1, 2, and 3 cutting times in order. Also, dry matter yield of sorghum~sudangrass hybrid was no significant difference between heading and headless type. Dry matter yield of first cutting plot in heading type and in headless type was the higher than those of second and third cutting plot. Acid detergent fiber and neutral detergent fiber of headless type were slightly higher than that of heading type. Acid detergent fiber of sorghumxsudangrass hybrid was highest at first cutting plot in both varieties. Neutral detergent fiber of second cutting plot in heading type and first cutting plot in headless type were the highest respectively. In vitro dry matter digestibility of headless type was very slightly higher than that of heading type. And in vitro dry matter digestibility of second cutting plot was the highest in both varieties. In vitro digestible dry matter of sorghumxsudangrass hybrid was no significant difference among treatments. The results demonstrated that although there was not significant difference, cultivation of headless type and first cutting plot per a year were very good for nutritive value and DM yield of sorghumxsudangrass hybrid as summer forage crops in Korea. (Key words : Heading, Headless type, Cutting frequency, Sorghum X Sudangrass Hybrid)

• Journal of the Korea Concrete Institute
• /
• v.17 no.4 s.88
• /
• pp.543-550
• /
• 2005

In the present work, modulus of rupture (MOR), flexural toughness properties $(I_{30}\;and\;W_{2.0})$ and workability (slump) of high performance hybrid fiber reinforced concrete (HPHFRC) mixed with micro-fiber (carbon fiber) and macro-fiber (steel fiber), and replaced with a fine mineral admixture such as silica fume (SF) are characterized through the analysis of variance (ANOVA). Data of MOR, $I_{30}(or W_{2.0})$ and slump are used as the characteristic values to estimate flexural performance and workable property of HPHFRC. Specially, an experimental design was Planned according to the fractional orthogoanl nay method to reduce experimental number of times. The experimental results show that steel fiber is a considerable significant factor in MOR and I30 $(W_{2.0})$. Based on the significance of experimental factors about each characteristic factors, the following evaluation can be used: Experiment factors which reduce slump most remarkably are carbon fiber, steel fiber, silica fume order.; Those that improve MOR most significantly are silica fume $({\fallingdotseq}\;carbon\;fiber)$, steel fiber order; Those that increase flexural toughness most distinctly are silica fume, carbon fiber, steel fiber order. It is obtained that the combination of steel fiber $1.0\%$, carbon fiber $0.25\%$ and silica fume $5.0\%$ is the experimental condition that improve MOR and flexural toughness excellently with workability ensured within the experiment.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.20 no.10
• /
• pp.72-79
• /
• 2021

A circular saw is an effective tool for cutting glass and carbon-fiber hybrid composites. This study investigated tool wear and cut quality when reusing saw blades. The carbide saws wear four times faster than the new ones, and polycrystalline diamond (PCD) is very resistant to tool wear, except at the end of its lifespan. The cut cross-section quality is affected by the blade type, tool wear, and spindle speed. Alternate top bevel (ATB)-type blades are suitable for cutting fiber-reinforced plastics, but triple-chip grind (TCG)-type blades are unsuitable because they cause fiber-pullout defects. Tool wear and low spindle speeds increase the occurrence of arc scratches, due to the rear saw blade. A microscopic examination showed that the burr, which is a mixture of fiber chips and epoxy matrix, was bonded on top, and glass-fiber delamination occurred on the bottom glass-fiber-reinforced polymer (GFRP) surface.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.19 no.2
• /
• pp.160-169
• /
• 2015

In this study, experimental research was carried out to improve the seismic performance of reinforced concrete exterior beam-column joint regions using replacing recycled coarse aggregate with hybrid fiber (steel fiber+PVA fiber) in existing reinforced concrete building. Therefore it was constructed and tested seven specimens retrofitting the beam-column joint regions using such retrofitting materials. Specimens, designed by retrofitting the beam-column joint regions of reinforced concrete building, were showed the stable failure mode and increase of load-carrying capacity due to the effect of crack control at the times of initial loading and bridge of retrofitting hybrid fiber during testing. Specimens BCJGPSR series, designed by the retrofitting of replacing recycled coarse aggregate with hybrid fiber in reinforecd beam-column joint regions were increased its maximum load carrying capacity by 1.01~1.04 times and its energy dissipation capacity by 1.06~1.29 times in comparison with standard specimen BCJS. Also, specimen $BCJGPSR_1$ were increased its energy dissipation capacity by 1.33~1.65 times in comparison with specimens BCJS, BCJP and BCJGPR series for a displacement ductility of 9.

• Polymer Science and Technology
• /
• v.21 no.2
• /
• pp.141-148
• /
• 2010

• Proceedings of the Optical Society of Korea Conference
• /
• 2009.02a
• /
• pp.489-489
• /
• 2009

• Journal of Korean Society of Water and Wastewater
• /
• v.24 no.3
• /
• pp.287-293
• /
• 2010

In this study, the toluene gas in VOCs was removed using bioreactor which applied with hollow fiber membrane and Pseudomonas sp. TDB-4. The EBRT of each reactor are controlled 60 sec(R-1) and 30 sec(R-2) and inlet tolune concentration of both R-1 and R-2 is controlled from 25ppm to 500 ppm. Up to 500 ppm of toluene concentration, the toluene removal efficiency of R-1 and R-2 are 92% and 81%, and theirs removal capacities are about 100 g/$m^3$/hr and 180 g/$m^3$/hr, respectively. In addition, according to this study, toluene removal efficiencies at the hollow fiber are approximately 70%(60 sec) and 45%(30sec).

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2000.04a
• /
• pp.67-70
• /
• 2000

Mechanical properties of (10%$AI_20_3{\cdot}SiO_2$+5%Ni)/Al hybrid composites fabricated by the reaction squeeze casting were compared with those of (15%$AI_20_3{\cdot}SiO_2$)/Al composites. Intermetallic compound formed by reaction between molten aluminum and reinforcing powder was uniformly distributed in the Al matrix. These intermetallic compounds were identified as $Al_3$NI using EDS and X-ray diffraction analysis. Microhardness and flexural strength of hybrid composites were higher than that of (15%$AI_20_3{\cdot}SiO_2$)/Al Composite. In-Situ fracture tests were Conducted on (15%$AI_20_3{\cdot}SiO_2$)/Al Composites and (10%$AI_20_3{\cdot}SiO_2$+5%Ni)/Al hybrid composites to identify the microfracture process. It was identified from the in-situ fracture test of (10%$AI_20_3{\cdot}SiO_2$+5%Ni)/Al composites, microcracks were initiated mainly at the short fiber / matrix interfaces. As the loading was continued, the crack propagated mainly along the separated interfacial regions and the well developed shear bands. It was identified from the in-situ fracture test of (10%$AI_20_3{\cdot}SiO_2$+5%Ni)/Al hybrid composites, microcracks were initiated mainly by the short fiber/matrix interfacial debonding. The crack proceeded mainly through the intermetallic compound clusters