• Structural Engineering and Mechanics
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• v.61 no.5
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• pp.675-684
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• 2017

In this paper, a hybrid seismic response control (HSRC) system was developed to control bridge behavior caused by the seismic load. It was aimed at optimum vibration control, composed of a rubber bearing of passive type and MR-damper of semi-active type. Its mathematical modeling was driven and applied to a bridge model so as to prove its validity. The bridge model was built for the experiment, a two-span bridge of 8.3 meters in length with the HSRC system put up on it. Then, inflicting the EI Centro seismic load on it, shaking table tests were carried out to confirm the system's validity. The experiments were conducted under the basic structure state (without an MR-damper applied) first, and then under the state with an MR-damper applied. It was also done under the basic structure state with a reinforced rubber bearing applied, then the passive on/off state of the HSRC system, and finally the semi-active state where the control algorithm was applied to the system. From the experiments, it was observed that pounding rather increased when the MR-damper alone was applied, and also that the application of the HSRC system effectively prevented it from occurring. That is, the experiments showed that the system successfully mitigated structural behavior by 70% against the basic structure state, and, further, when control algorithm is applied for the operation of the MR-damper, relative displacement was found to be effectively mitigated by 80%. As a result, the HSRC system was proven to be effective in mitigating responses of the two-span bridge under seismic load.

• Journal of the Korean GEO-environmental Society
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• v.4 no.2
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• pp.27-37
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• 2003

In this research stress-strain behavior of composite geocell-soil systems under triaxial condition and the influence of strength due to the presence of geocell were studied. For the research a series of triaxial tests were carried out on sand specimens confined by flexible-walled single rubber cell. The diameter of all rubber cells placed at the center of the soil sample were 50 mm. Three rubber sizes, i.e. 35, 50 and 70 mm height, were applied to the soil specimen and the size of soil specimen was 50 mm in diameter and 100 mm in height. Three different densities of soil were used for the tests. In general, it was observed that the sand specimen develops an apparent cohesion due to the confinement by the geocell. The magnitude of this cohesion seemed to be dependent to the properties of the geocell material. The test results have shown that the geocell material for this research not only develops the apparent cohesion but also increases the angle of friction whereas geosynthetic material in the references showed only the increase of apparent cohesion. From the application of geocell-soil composites to the hyperbolic model, it was recognized that the determination of the peak strength influences the behavior of the geocell-soil composites.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.12
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• pp.1465-1471
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• 2013

The electrical and mechanical properties of room temperature vulcanized (RTV) silicone rubber composites are investigated as functions of multi-walled carbon nanotube (CNT), carbon black (CB), and thinner content. The thinner is used to improve the CNT and CB dispersion in the matrix. The electrical and mechanical properties of the composite with CNT are improved when compared to the composite with CB at the same content. As the thinner content is 80 phr, the electric resistance of the composite decreases significantly with the CNT content and shows contact point saturation of CNT at 2.5 phr. As the thinner content increases, the dispersion of conductive particles improves; however, the critical CB content increases because of the reduction in the CB weight ratio. It is believed that an electrode that needs good flexibility and excellent electrical properties can be manufactured when the amount of CNT and CB are increased with the thinner content.

• Applied Chemistry for Engineering
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• v.27 no.2
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• pp.179-184
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• 2016

In this work, the influence of milled carbon fiber direction on mechanical properties of milled carbon fibers/carbon blacks/natural rubber compounds was investigated. The compounds were prepared by adding the 6 phr milled carbon fibers (MCFs) and 40 phr carbon blacks (CBs) into the natural rubber. The MCFs were aligned in a parallel and orthogonal direction in the compounds using two-roll-mill machine. Mechanical properties of compounds were studied by tensile characteristics and tearing strength. As a result, the compounds showed higher tensile strength, 100%~300% modulus, and tearing strength than those of using any other compounds due to the aligning MCFs in parallel. Mechanical properties of the compounds reinforced with non-aligned MCFs were inferior to those of others. Consequently, the parallel aligned MCFs in the compounds led to an increase of tensile properties and improvement of tearing strength, resulted from MCFs with the high elastic modulus.

• Journal of Adhesion and Interface
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• v.19 no.2
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• pp.60-67
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• 2018

In the present study, when the surface of kenaf, which is an environmentally friendly natural fiber, was treated by using adhesive solution containing Chemlok 402, the effects of fiber surface treatment, fiber content and fiber length on the cure characteristics, hardness, tensile modulus and abrasion resistance of kenaf/natural rubber composites were investigated. The kenaf fiber contents consisting of the composites were varied with 0, 5, 10, 15, and 29 phr at a fixed fiber length of 2 mm and also the fiber length was varied with 2, 35, and 70 mm at a fixed fiber content of 5 phr. The Tmax and tc90 values, Shore A hardness, tensile modulus, and abrasion resistance of natural rubber composites strongly depended on the kenaf fiber content and length. The characteristics of the composite with kenaf fibers treated with the adhesive solution containing Chemlok 402 were higher than those untreated. This is ascribed to the improved interfacial adhesion between the treated kenaf fiber and the rubber matrix. This study suggests that an appropriate use of adhesive solution may be possible to increase the properties of natural fiber-reinforced composites.

• Journal of Adhesion and Interface
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• v.22 no.4
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• pp.118-127
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• 2021

In this study, the mechanical properties of vulcanized rubber were evaluated through compounding by controlling filler content to improve the mechanical properties of NBR rubber. Aramid and glass fibers with excellent heat resistance were used as fillers, and ceramics were additionally used in anticipation of a complementary effect, and as for the ceramic materials, needle-shaped and plate-shaped ceramics were used. Each filler was used in an amount of 5.0, 10.0, 15.0, and 20.0 phr in order to investigate the basic properties according to the amount of filler. To confirm the complementary effect through ceramic application, each 10.0 phr fiber and ceramic were mixed with 1:1 ratio to evaluate mechanical properties. As a result, it was confirmed that the decreasing ratio of tensile strength after heat aging was small in the order of aramid fiber, acicular ceramic, glass fiber, and plate ceramic in the case of applying the filler alone. In addition, the mechanical characteristics of vulcanized rubber using composite filler based on fibers and ceramics were evaluated, and it was confirmed that the composite filler had a complementary effect on thermal aging.

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.190-198
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• 2002

In this research the physical properties of polymer modified mortar containing pulverized FRP(Fiber-Reinforced Plastics) wastes fine powder as a part of fine aggregate were investigated. Styrene-butadiene rubber(SBR) latex, polyacrylic ester(PAE) emulsion and ethylene-vinyl acetate(EVA) emulsion were used as Polymer modifier. Polymer modified mortars containing FRP wastes fine powder were prepared with various FRP wastes fine powder replacement(5∼30 wt％) for fine aggregate and polymer-cement ratios(5∼20 wt％). The water-cement ratio, water absorption rates and hot water immersion test, compressive and flexural strengths of polymer modified mortars were tested and the results compared to those of ordinary portland cement mortar. As the results, compressive and flexural strengths of polymer modified mortar containing FRP wastes fine powder depend on the contents of FRP wastes fine powder, type and additional amounts of polymer modifier. Some of them showed higher compressive and flexural strengths than those of ordinary portland cement mortar. Especially, SBR-modified mortar showed the highest strengths properties among three types of polymer modifier. Also water absorption rates, compressive and flexural strengths of SBR-modified mortar were more superior than those of PAE or EVA-modified mortar. The optimum mix proportions of SBR-modified mortar was 20 wt％ of polymer-cement ratio and 20 wt％ of FRP wastes fine powder replacement. Otherwise heat cured polymer modified mortar accelerated the improvement of early compressive and flexural strengths.

• Elastomers and Composites
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• v.41 no.4
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• pp.260-267
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• 2006

SBR (styrene-butadiene rubber; 25 wt% of solid contents) nanocomposites reinforced with OLS(organically modified layered silicates) were manufactured via the latex method. Two types of OLS are prepared, i.e. dodecylamine (primary amine) modified montmorillonite (DA-MMT) and N, N-dimethyldodecylamine (tertiary amino) modified MMT (DDA-MMT). X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed to characterize the layer distance of OLS and the morphology of the nanocomposites. SBR nanocomposites reinforced with ternary phase filler (carbon black/silica/OLS) systems also manufactured. Dynamic mechanical thermal analysis (DMTA) was performed on these composites to determine the loss factor (tan $\delta$) over a range of temperature($-20^{\circ}C{\sim}80^{\circ}C$). The results showed that there was significant changes on the values or tan $\delta$ with the addition of small amount of the OLS. By increasing the contents of OLS, the values of tan $\delta$ at $0^{\circ}C$ increased but those of tan $\delta$ at $60^{\circ}C$ decreased with increasing OLS contents.

• Journal of Ocean Engineering and Technology
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• v.17 no.4
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• pp.37-42
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• 2003

The mechanical components with high-pressure hoses are generally produced by the swaging process. The hoses are composed of the rubber materials and the reinforced braids to support tensile forces. In case they are subjected to high mechanical and thermal loads under severe operating conditions, the oil in hoses can leak at the parts of small clamping forces. In this paper, the deformation characteristics of a fiber-reinforced hose are analyzed with respect to the jaw strokes using the finite element method. The manufacturing process is modeled with a contact problem in consideration of a real situation, and the material properties based on the experimental results are used in the analysis. Examinations of the relationship between the swaging strokes and the deformation behaviors of the hose were made on the basis of the stress and strain values of the hose components. The relations between clamping forces and separating forces are also proposed, in order to estimate clamping forces corresponding to separating forces for the given model.

• Advances in materials Research
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• v.4 no.3
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• pp.165-178
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• 2015

Friction coefficient of epoxy metal matrix composites were investigated. The main objective was to increase the friction coefficient through rubber sole sliding against the epoxy floor coating providing appropriate level of resistance. This was to avoid the excessive movement and slip accidents. Epoxy metal matrix composites were reinforced by different copper wire diameters. The epoxy metal matrix composites were experimentally conducted at different conditions namely dry, water and detergent wetted sliding, were the friction coefficient increased as the number of wires increased. When the wires were closer to the sliding surface, the friction coefficient was found to increase. The friction coefficient was found to increase with the increase of the copper wire diameter in epoxy metal matrix composites. This behavior was attributed to the fact that as the diameter and the number of wires increased, the intensity of the electric field, generated from electric static charge increased causing an adhesion increase between the two sliding surfaces. At water wetted sliding conditions, the effect of changing number of wires on friction coefficient was less than the effect of wire diameter. The presence of water and detergent on the sliding surfaces decreased friction coefficient compared to the dry sliding. When the surfaces were detergent wetted, the friction coefficient values were found to be lower than that observed when sliding in water or dry condition.