• Proceedings of the KSME Conference
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• 2001.11a
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• pp.703-709
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• 2001

In this paper, we analyzed the laminated composite sandwich plate structure of truss core with changing values of the designing parameters. As a result, in designing parameters of that, the more height and thickness of the laminated composite plate's core, the more increase of natural frequency. In this type of structure, in the case of applying core of the laminated composite plate and antisymmetric stacking, natural frequency has high value and we calculated the optimum angle-ply making natural frequency maximum. Natural frequency of CFRP is higher than that of GFRP. Both are materials of the laminated composite plate. The mode shapes are various along with the angle-ply of the laminated composite plate.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.710-715
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• 1997

This paper deals with the analysis of the optimum value of honeycomb core considering variable design parameter. As thickness and height of core rises in design parameter, natural frequency of laminated composite plate increases. The angle-phy has the maximum value when the plate of honeycomb core join to opposite direction. This paper shows that the natural frequency of CFRP was higher than that of GFRP and mode shapes were various at angle-ply.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.2
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• pp.202-206
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• 2011

Works on the strength and stiffness in the structural members are carried out widely with various material and cross-sections with ever increasing safety concerns, they are presently applied in various fields including railroad trains, air crafts and automobiles. In addition to this, problem of lighting structural members became important subject by control of exhaust gas emission, fuel economy and energy efficiency. So, Light weight of member structures is necessary for the high performance and various functions. In this study, the CFRP flat and circular member was manufactured by CFRP prepreg sheet in autoclave. Carbon FRP is an anisotropy material whose mechanical properties change with its fiber orientation angle, so this study apply to the effects of the fiber orientation angle on the bending characteristics of the member. Each CFRP flat and circle are compared by strength and stiffness.

• Journal of KSNVE
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• v.5 no.2
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• pp.215-224
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• 1995

In this paper, the three-dimensional finite element model is established to investigate the structural dynamic characteristics of rotor blade using a finite element analysis. Six natural frequencies and mode shapes are calculated by computer simulation. The first three flapping modal frequencies, the first two lead-lag modal frequencies, and the first feathering modal frequency are validated through comparison with the modal test results of the fixed rotor blade. The computer simulation results are found in good agreement with experimentally measured natural frequencies. The important results are obtained as follows: (1) Natural frequencies are changed due to the variation of rotational speed and fiber angle of rotor blade, (2) Weak coupling between flapping mode shape and lead-lag mode shape are detected, (3) Centrifugal force has more effect on flapping modal frequency than lead-lag modal frequency.

• Current Optics and Photonics
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• v.6 no.2
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• pp.196-201
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• 2022

Collagen fibers tens of nanometers in size, which constitute most of the corneal volume of the human eye, are layered in a uniform direction, and adjacent fiber layers are arranged at an angle of 90° to each other. According to the results of this study, the transmittance at 45° of interlayer rotation angle is highest, and higher than that of the 90° body structure. The transmittance is examined, concerning the polarization state of the incident light; circularly polarized light case shows higher transmittance than linearly polarized. Through this, a simulation to confirm the deformed structure of collagen fibers, which show higher transmittance than the anatomical structure of the cornea, is attempted.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.108-111
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• 2004

The polypropylene(PP) fiber is poised as a low cost alternative for reinforcement in structural applications in comparison with other high performance fibers, such as the polyvinyl-alcohol(PVA), polyethylene, carbon and aramid fiber. The mechanical properties of the composite are strongly determined by the interfacial behavior of fiber and cementitious matrix. The crack bridging mechanism contribute to composite toughness from activation of the fiber-matrix interface where energy is dissipated through debonding of the interface and fiber pullout. In this study, therefore, the pullout behavior of PP fibers is investigated. Experimental work includes the investigation of the interfacial properties, and the composite property. The quantification of interfacial properties, the frictional bond is achieved through single fiber pullout test. A study on the effect of inclination angle on fiber pullout behavior is also conducted.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.433-440
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• 2001

This study was to analyze characteristics of soils reinforced by FPF(Fibrillated Polypropylene Fiber). Laboratory test, model test and field tests were performed on soils reinforced by fibers, to evaluate the shear strength characteristics. For the silty sand, clayey sand and silty clay, the influence of fiber shape, fiber length and fiber content were evaluated from compaction test, direct shear test, uniaxial test, california bearing ratio(CBR) test. Fibrillated type fiber, 5cm long with a content of 0.5% shows 5∼30% increase of friction angle and 7∼55 percent increase of CBR value.

• Textile Coloration and Finishing
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• v.33 no.4
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• pp.309-316
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• 2021

Due to the rigid nature of the silicon carbide fiber(SiC), fiber damage occurs from the friction during the carding process. This damage not only lowers the spun yarn yield, but also lowers the heat resistance of the spun yarn, so that ultra-high heat resistant yarn cannot be manufactured. Therefore, in the carding process where the most friction between fiber and machine(wire, etc.) occurs, some factors were modified and tested, and as a result of measuring the change in physical properties, fiber damage decreased due to the wire angle or wire density, resulting in improved yield. The test method used to measure the yield of SiC fiber was the carbonization method, and the content of SiC fibers was calculated using the remaining amount after carbonization. Carbonization test was performed at air condition, 700℃, and for 2 hours. Analysis by SEM-EDX showed that the carbide was consistent with the composition of the SiC fiber.

• Fibers and Polymers
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• v.4 no.4
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• pp.161-168
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• 2003

An investigation of the dimensionless torque in the newly developed cone drum twister texturing mechanism is reported. The cone drum twister is one of the outer surface contacting friction-twisting devices in false-twist texturing. In this cone drum twister, a filament yam passes over the surface of the cone drum that rotates by the passing yarn without a special driving device. This research is composed of the theoretical analysis of the false twisting mechanism and the experimental analysis at room temperature. The equations have been derived which shows interrelationship of the conical angle of cone drum, the wrapping angle, the drag angle, and the yam helix angle. Theoretical values of dimensionless torque were calculated and were compared with the experimental results. It is shown that, as the conical angle and the projected wrapping angle increased, the dimensionless torque also increased. But the conical angle was reached to ${30.75}^{\circ}C$, the dimensionless torque decreased.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.224-224
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• 2012

For decades, carbon fiber has expanded their application fields from reinforced composites to energy storage and transfer technologies such as electrodes for super-capacitors and lithium ion batteries and gas diffusion layers for proton exchange membrane fuel cell. Especially in fuel cell, water repellency of gas diffusion layer has become very important property for preventing flooding which is induced by condensed water could damage the fuel cell performance. In this work, we fabricated superhydrophobic network of carbon fiber with high aspect ratio hair-like nanostructure by preferential oxygen plasma etching. Superhydrophobic carbon fiber surfaces were achieved by hydrophobic material coating with a siloxane-based hydrocarbon film, which increased the water contact angle from $147^{\circ}$ to $163^{\circ}$ and decreased the contact angle hysteresis from $71^{\circ}$ to below $5^{\circ}$, sufficient to cause droplet roll-off from the surface in millimeter scale water droplet deposition test. Also, we have explored that the condensation behavior (nucleation and growth) of water droplet on the superhydrophobic carbon fiber were significantly retarded due to the high-aspect-ratio nanostructures under super-saturated vapor conditions. It is implied that superhydrophobic carbon fiber can provide a passage for vapor or gas flow in wet environments such as a gas diffusion layer requiring the effective water removal in the operation of proton exchange membrane fuel cell. Moreover, such nanostructuring of carbon-based materials can be extended to carbon fiber, carbon black or carbon films for applications as a cathode in lithium batteries or carbon fiber composites.