• Composites Research
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• v.15 no.2
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• pp.18-23
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• 2002

The absorption and the interference shielding of the problems thor both commercial and military purposes. In this study, the minimization of the electromagnetic wale reflections using composite layers with different dielectric properties was performed. Dielectric constants were measured for glass/epoxy composites containing conductive carbon blacks and carbon/epoxy fabric composites. Using the measured permittivities of the composites having various carbon black contents, the optimal electromagnetic wave absorbing structure in X-band(8.2GHz-12.4GHz) was determined. The optimal multi-layered composite plates have the thickness of 2.6mm. The maximum reflection loss is -30dB at 10GHz, and the bandwidth haying the absorptivity lower than -l0dB is about 2GHz.

• Composites Research
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• v.17 no.2
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• pp.1-8
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• 2004

The present paper is concerned with the optimum design of taper spring, in which the static spring rate of the fiber-reinforcement composite material spring is fitted to that of the steel leaf spring. The thickness and width of springs were selected as design variables. The object functions of the regression model were obtained through the analysis with a common analytic program. After regression coefficients were calculated to get functions of the regression model, optimal solutions were calculated with DOT. E-glass/epoxy and carbon/epoxy were used as fiber reinforcement materials in the design, which were compared and analyzed with the steel leaf spring. The result of the static spring rates show that optimized composite leaf springs agree with steel leaf spring within 1%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.2
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• pp.426-434
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• 2010

This study is experimentally performed to evaluate the strength reduction behavior and its statistical properties of plain woven glass/epoxy composites. The results indicate that the major impact damage of plain woven glass/epoxy composites is the fiber breakage and matrix crack, whereas the dominant impact damage of unidirectional carbon/epoxy laminates is the delamination, which depends on the stacking sequence. The residual strength prediction models, previously proposed on unidirectional laminates, are applied to evaluate the residual strength of plain woven glass/epoxy composites with impact damage. Among these models, the results by Caprino and Avva's model have a good agreement with the experimental results. To investigate the variability of residual strength of the impacted composite materials, a statistical model was proposed and its results were in conformance with the experimental results regardless of their thickness.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2853-2865
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• 2000

During the curing process of thick glass/epoxy laminates, a substantial amount of temperature lag and overshoot at the center of the laminates is usually experienced due to the large thickness and low thermal conductivity of the glass/epoxy composites. Also, it takes a longer time for full and uniform consolidation. In this work, temperature, degree of cure and consolidation of a 20 mm thick unidirectional glass/epoxy laminate were investigated using an experiment and a 3-dimentional numerical analysis. From the experimental and numerical results, it was found that the experimentally obtained temperature profile agreed well with the numerical one, and the cure cycle recommended by the prepreg manufacturer should be modified to prevent a temperature overshoot and to obtain full consolidation.

• Journal of the Korean Society for Precision Engineering
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• v.7 no.4
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• pp.29-39
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• 1990

The purpose of this research is to analyze the impact behaviors of laminated composite plates subjected to the transverse low-velocity impact by the steel ball. A plate finite element model based on Whitney and Pagano's the first-order shear deformation theory (FSDT) in conjunction with experimental static contact laws is formulated and then compared with the results of the impact experiments. Because the input data and the output data printed at every integration time step are lots of amount, these are interactively poecessed by the developed pre-processor(PREPLOT) and postprecessor(POSTPLOT). All results from these procesors are automatically generated by CALCOMP plotter. Test materials are glass/expoxy composite materials. The specimens are composed of [$0^{\circ} /45^{\circ}/0^{\circ}/-45^{\circ}/0^{\circ}/]2s\ and \[90^{\circ}/45^{\circ}/90^{\circ}/-45^{\circ}/90^{\circ}/$]2s stacking sequences and have $4.5^t{\times}200^w{\times}200^l$(mm) and $4.5^t{\times}300^w{\times}300^l$(mm) dimensions.

• Advanced Composite Materials
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• v.18 no.3
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• pp.209-219
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• 2009

Carbon nanotubes (CNTs) have shown great potential for the reinforcement of polymers or fiber-reinforced composites. In this study, mechanical properties of multi-walled carbon nanotube (MWNT)-filled plain-weave glass/epoxy composites intended for use in radar absorbing structures were evaluated with regard to filler loading, microstructure, and fiber volume fraction. The plain-weave composites containing MWNTs exhibited improved matrix-dominant and interlaminar fracture-related properties, that is, compressive and interlaminar shear strength. This is attributed to strengthening of the matrix rich region and the interface between glass yarns by the MWNTs. However, tensile properties were only slightly affected by the addition of MWNTs, as they are fiber-dominant properties.

• 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.

• Proceedings of the Materials Research Society of Korea Conference
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• 1996.05a
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• pp.125-125
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• 1996

• Proceedings of the Materials Research Society of Korea Conference
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• 1996.11a
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• pp.120-120
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• 1996

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.187-190
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• 2000

Cyclocopter is air vehicle to vertically take-off and land like a helicopter. This is an efficient and quiet means of being able to direct thrust compared to a helicopter. The rotor consists of several blades rotating about a horizontal axis perpendicular to the direction of normal flight. The direction of blade span is parallel to rotating axis and both end roots are connected to the hub to resist centrifugal force and to transmit the power. The pitch of the individual blades to the tangent of the circle of the blade's path is varied cyclically to gain thrust. In the paper, the design and manufactures of cyclocopter rotor blades are presented. Stress at the roots of cyclocopter blades is great due to centrifugal and aerodynamic forces and aeroelastic instabilities appear. The blades consist of main spar, front spar, polyurethan foam, weight, and skin and spars and skin are made of glass/epoxy composite.