• Composites Research
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• v.26 no.3
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• pp.155-159
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• 2013

This paper reviewed the continuous fiber tow spreading technologies and its applications. The effect of the continuous fiber tow spreading in manufacturing process of continuous fiber reinforced thermoplastic composite was introduced theoretically. The fiber tow spreading technologies were categorized according to the spreading medium and its order during manufacturing process. The general principles, the applications, and the merits and demerits of fiber tow spreading technologies were introduced. Furthermore, the proposal for future direction of research on this issue was considered in this study.

• Composites Research
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• v.12 no.3
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• pp.75-83
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• 1999

The thermal properties of carbon/phenolic and silica/phenolic ablative composites were investigated by measuring the heat capacity, thermal diffusivity and thermal conductivity. The heat capacities of carbon/ phenolic and silica/phenolic composites were calculated from differential scanning calorimeter curve. The thermal diffusivities of carbon/phenolic and silica/phenolic composites were measured by the laser flash method with varying laminated direction, i.e., with laminar direction and across laminar direction. The thermal diffusivities decreased with increasing temperature. The thermal conductivities of carbon/phenolic and silica/phenolic composites were calculated using the heat capacity, density and thermal diffusivity. The thermal conductivities increased with increasing temperature. The thermal conductivity of with laminar direction is two times higher than that of across-laminar direction in carbon/phenolic composite due to the directionality of thermal conductivity of carbon fiber. The thermal conductivities of two dimensional fiber reinforced composites were analyzed using the conductivities of constituents and volume fraction of each constituent. The thermal conductivities of carbon fiber and silica fiber were calculated from thermal conductivities of carbon/phenolic and silica/phenolic composites. The thermal conductivities of carbon/phenolic and silica/phenolic composites at RT were predicted from thermal conductivities of fiber and resin with varying the volume fraction of fiber.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.04b
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• pp.3-24
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• 2000

이 글에는 문화사적으로 고려한 건설공학의 위치와 구조물의 제 5 기본 개념으로서의 복합재료 그리고 건설 재료로서의 섬유 복합재료의 대두는 역사적인 필연성에 의한 것임이 설명되어 있다. 여러 나라에서의 섬유 복합재료의 건설에 대한 응용 현황과 여러 학계의 움직임이 설명되고 앞으로의 연구방향이 간략하게 설명되어 있다.

• Composites Research
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• v.26 no.3
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• pp.189-194
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• 2013

This paper deals with the study of mechanical properties and impact energy absorbed by composites, made by using thermoplastic and thermoset as matrix, flax fiber and nanoclay as reinforcements. The nanoclay was sprayed on the fiber laminate directly after mixing with ethanol. This experiment designed by Taguchi method and have variable factors, i.e three types of fiber direction(F), three different nanoclay wt%(N) and three spray gun hole shapes(S). According to these conditions, composites were made and the optimum conditions were found to be F1N3S1, F1N2S1, F1N2S1 and F3N2S1 for thermoplastic, and F1N3S2, F1N3S2, F1N2S2 and F3N2S1 for thermoset which were matched with tensile strength, modulus, total impact absorbed energy and heat release rate respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.1
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• pp.29-36
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• 1991

The effects of heat treatment on fatigue crack growth behavior were studied in continuously reinfored, magnesium-based composite (FP/ZE41A). Following an earlier TEM investigation, specimens were thermally aged to modify the interfacial zone between the alumina fibers and mg alloy matrix. The fatigue crack growth experiments were conducted with specimens having the fiber orientation normal to the crack growth direction(longitudinal) and also specimens with the fibers oriented parallel to the crack growth direction(transverse). A comparision of the fatigue crack growth behavior indicates that aged longitudinal specimens are more resistant to fatigue crack growth than as-fabricated longitudinal specimens. Conversely, as-fabricated transverse specimens are more resistant to fatigue crack growth than aged transverse specimens. SEM observations of fiber pullout and ductile tearing on the fatigue fracture surfaces indicate that the aging weakens the strength of the fiber/matrix interface, giving rise to the observed fatigue crack growth behavior.

• Journal of the Korean Wood Science and Technology
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• v.42 no.4
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• pp.367-375
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• 2014

A simplified material model, which was efficiently implemented in a three-dimensional finite solid element (3D FE) analysis for wood was developed. The bi-linear elasto-plastic anisotropic material theory was adopted to describe constitutive relations of wood in three major directions including longitudinal, radial and tangential direction. The assumption of transverse isotropy was made to reduce the requisite 27 material constants to 6 independent constants including elastic moduli, yield stresses and Poisson's ratios in the parallel, and perpendicular to grain directions. The results of Douglas fir compression tests in the three directions were compared to the 3D FE simulation incorporated with the wood material model developed in this study. Successful agreements of the results were found in the load-deformation curves and the permanent deformations. Future works and difficulties expected in the advanced application of the model were discussed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.2
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• pp.447-455
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• 2014

This study was intended to estimate the efficiency of inducing fiber arrangement in UHPCC (Ultra High Performance Cementitious Composites). For the purpose, UHPCC members produced by several different placing methods according to flow characteristics were prepared; flexural behaviors were compared and correlation between the flexural behavior and the characteristics of fiber arrangement was investigated. Test results showed that placing method for inducing specific fiber arrangement had a considerable influence on the flexural performance. The standard specimen in which fibers are induced to be directed parallel to the principle tensile direction presented higher flexural tensile strength but lower variation. Therefore it should be considered that the flexural tensile strength actually developed in UHPCC member may be highly different and in lager variation. The qualitative variation of fiber arrangement according to the flow of UHPCC was also predicted considering the flow pattern and the boundary effect; the prediction provided good explanation to the difference in the flexural behavior according to the induced flow.

• Proceedings of the Korean Fiber Society Conference
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• 2001.10a
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• pp.359-360
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• 2001

헤테로고리 방향족 polybenzoxazole(PBO)은 대표적인 내열성 고분자로서, 고온에서의 열적안정성 및 내화학성, 기계적 물성, 방염성 등에서 우수한 성질을 나타낸다. 그러나 황산과 같은 강산에만 용해되기 때문에 가공성 면에서 단점을 가지고 있어 사용하는데 있어 제약이 따른단 현재 이러한 단점을 보완하기 위해 polyhydroxyamide(PHA)와 같은 전구체 고분자에 대한 연구가 많은 연구자들에 의해 진행되고 있다. (중략)

• Computational Structural Engineering
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• v.11 no.3
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• pp.229-239
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• 1998

복합재료는 강도-무게비가 다른 재료들에 비해 훨씬 크기 때문에 부재의 좌굴문제가 대단히 중요하게 취급되며, 본 논문에서는 축방향 압축력을 받는 복합재료로 된 쉘 부재의 좌굴해석이 수행된다. 이 재료는 일반적으로 이방성 재료 특성을 나타내 보이나, 섬유들이 한 방향으로만 배치되어 있는 경우 섬유방향에 연직한 평면에서의 강도나 탄성계수들은 모두 일정한 횡 등방성 재료성질을 가진 것으로 간주할 수 있다. 9 절점 degenerate 쉘 유한요소를 사용한 선형안정해석, LUSAS 범용 프로그램을 이용한 구조해석, 그리고 고전적 쉘 좌굴방정식에 의한 해석들을 수행하였으며, 그 결과들을 서로 비교, 분석하였다. 고려된 등방성 재료나 횡 등방성 재료의 경우 모두, degenerate 유한요소해석으로 계산한 임계하중들은 고전적 이론해에 의한 결과들 보다 낮았으며, LUSAS 결과들과는 거의 같았다. 이는 degenerate 유한요소에 의한 선형안정해석 결과들이 안전측에 듬을 의미하며, 복합재료로 된 쉘 구조물의 좌굴해석에 degenerate 유한요소를 효율적으로 적용할 수 있음을 의미한다.

• Korean Journal of Optics and Photonics
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• v.25 no.4
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• pp.207-215
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• 2014

In this paper the radial stiffness associated with stacking sequence effects, and the dimensional stability issue associated with thermally induced surface deformation in quasi-isotropic laminates due to the effect of stacking sequence and additional resin layer technique, are numerically investigated. Finally, the influence of surface resin layer techniques for fiber print-through mitigation in a composite mirror is tested for evaluation of surface accuracy across varying thermal conditions.