• 한국공간구조학회:학술대회논문집
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• 한국공간구조학회 2008년도 춘계 학술발표회 논문집
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• pp.113-118
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• 2008

This paper presents a flexural-torsional analysis of thin-walled open-section composite beams. A general geometrically nonlinear model for thin-walled composite beams and general laminate stacking sequences is given by using systematic variational formulation based on the classical lamination theory. The nonlinear algebraic equations of present theory are linearized and solved by means of an incremental Newton-Raphson method. Based on the analytical model, a displacement-based one-dimensional finite element model is developed to formulate the problem. Numerical results are obtained for thin-walled composite beams under general loadings, addressing the effects of fiber angle, laminate stacking sequence and loading parameters.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 춘계학술발표대회 논문집
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• pp.95-98
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• 2003

In this work, a closed-form analysis is performed to obtain the stiffness coefficients of thin-walled composites beams with elliptical profiles. The analytical model includes the effects of elastic couplings, shell wall thickness, torsion warping and constrained warping. Reissner's semi-complementary energy functional is used to derive the beam force-displacement relations. The theory is validated against MSC/NASTRAN results for coupled composites beams with single-cell elliptical sections. Very good correlation has been noticed for the test cases considered.

• 한국강구조학회 논문집
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• 제14권1호
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• pp.31-40
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• 2002

적층된 박벽 복합재료 보의 자유 진동에 관한 연구를 수행하였다. 박벽 C형강 복합재료의 동적 거동에 적용 가능한 일반적인 해석 모델을 개발하였다. 이 모델은 classical lamination theory를 기초로 두고 있으며, 임의의 적층 상태의 구성 즉, 대칭뿐만 아니라 비대칭의 적층 상태, 그리고 다양한 경계조건에 따른 휨과 비틀림 형상의 연계(coupling)을 설명하였다. 변위를 기반으로 한 일차원 유한 요소 모델은 박벽 복합재료 보의 고유 진동수와 그에 대응하는 진동 모드를 예측하기 위해 개발되었다. 운동방정식은 Hamiton의 원리로부터 유도되었으며, 수치적인 결과는 박벽 복합재 보에서 복합재료의 진동수와 모드 형상에 대해 적층각, 계수비, 그리고 경계조건의 영향을 얻을 수 있었다.

• Composites Research
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• 제30권6호
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• pp.406-409
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• 2017

The thin-walled cylindrical tubes are frequently used for the evaluation of fatigue property of composites. But the curvature of the tubular specimen induces interlaminar normal stress which may affect the fatigue property. In this paper interlaminar normal stress effect on the fatigue behaviour of thin-walled graphite/epoxy tubes $[{\pm}45]_s$ composites was studied experimentally. It was concluded that the interlaminar normal stress induced by the curvature of the cylinder has no discernible effect on the fatigue life. But excessive internal pressure can produce the stiffness increase and this affects the fatigue life of the cylindrical tubular composite.

• Composites Research
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• 제17권5호
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• pp.7-14
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• 2004

본 연구에서는 끝단에 질량이 부착된 복합재료 박판 보의 동특성을 제어하기 위하여 퍼지 알고리즘을 이용한 적응 제어 기법에 대하여 고찰하였다. 적응제어기법을 구현하기 위해 감지기와 작동기의 역할을 할 수 있는 압전재료를 구조물의 중립면상에 삽입하였다. 끝단 질량이 변하는 경우, 비례제어 및 속도제어와 비교해 볼 때, 퍼지 알고리즘을 이용한 제어 기법이 복합재료 박판 보의 동적응답제어에 우수한 성능을 보였다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1443-1446
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• 2005

We have synthesized thin multi-walled carbon nanotubes (t-MWCNTs) using a catalytic chemical vapor deposition (CCVD) method with FeMoMgO catalyst. The number of tube walls were 2 ${\sim}$ 6 with the corresponding diameters of 3 ${\sim}$ 6 nm. We obtained high production yield of over 3000 wt% compared to the weight of the supplied catalyst. These t-MWCNTs revealed the intermediate structural characteristics between single- and multi-walled carbon nanotubes (SWCNTs and MWCNTs). We have also characterized the field emission properties such as turn-on field and emission current, and current degradation from these t-MWCNTs together with SWCNTs and MWCNTs.

• 한국철도학회논문집
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• 제9권1호
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• pp.57-62
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• 2006

Composite thin-walled members for civil engineering application are mainly produced by pultrusion technique, and they are generally made of a polymeric resin system reinforced by E-glass fibers due to economical reason. This material combination results in low elastic moduli of the composite materials and makes the design of composite members to be governed by stability limit state. Therefore the buckling behavior of composite thin-walled members was experimentally investigated in the present study. Axial compression was applied on each specimens by a hydraulic ram and knife edge fixtures were placed at both ends to simulate simple boundary condition. Axial compression, lateral displacements and twisting at the mid-height of each specimen were measured by a set of transducers during buckling test. The experimental buckling loads were compared with analytical results obtained through isotropic formulas. In the calculation of analytical results, elastic properties such as Young's modulus(E) and shear modulus(G) were replaced with EL and GLT obtained from coupon tests, respectively.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 봄 학술발표회 논문집
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• pp.489-496
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• 2002

The lateral buckling of a laminated composite beam is studied. A general analytical model applicable to the lateral buckling of a composite beam subjected to various types of loadings is derived. This model is based on the classical lamination theory, and accounts for the material coupling for arbitrary laminate stacking sequence configuration and various boundary conditions. The effects of the location of applied loading on the buckling capacity are also included in the analysis. A displace-based one-dimensional finite element model is developed to predict critical loads and corresponding buckling modes for a thin-walled composite beam with arbitrary boundary conditions. Numerical results are obtained for thin-walled composites under central point load, uniformly distributed load, and pure bending with angle-ply and laminates. The effects of fiber orientation location of applied load, and types of loads on the critical buckling loads are parametrically studied.

• Composites Research
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• 제30권1호
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• pp.7-14
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• 2017

In this paper, the inter-lamina shear strength (ILSS) of multi-wall carbon nanotube (MWNT) reinforced carbon fiber reinforced plastics (CFRP) and thin-ply composites were verified under low earth orbit (LEO) space environment. CFRP, MWNT reinforced CFRP, thin-ply CFRP and MWNT reinforced thin-ply CFRP were tested after aging by using accelerated ground simulation equipment. The used ground simulation equipment can simulate high vacuum ($2.5{\times}10^{-6}torr$), atomic oxygen (AO, $9.15{\times}10^{14}atoms/cm^2{\cdot}s$), ultraviolet light (UV, 200 nm wave length) and thermal cycling ($-70{\sim}100^{\circ}C$) simultaneously. The duration of aging experiment was twenty hours, which is an equivalent duration to that of STS-4 space shuttle condition. After the aging experiment, ILSS were measured at room temperature ($27^{\circ}C$), high temperature ($100^{\circ}C$) and low temperature ($-100^{\circ}C$) to verify the effect of operation temperature. The MWNT and thin-ply shows good improvement of ILSS at ground condition especially with the thin-ply. And after LEO exposure large degradation of ILSS was observed at MWNT added composite due to the thermal cycle. And the degradation rate was much higher under the high temperature condition. But, at the low temperature condition, the ILSS was largely recovered due to the matrix toughening effect.

• Composites Research
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• 제15권3호
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• pp.18-29
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• 2002

본 논문에서는 얇은 벽보로 모델링 한 위성체 구조물에 입사되는 열 하중에 의해 발생하는 굽힘 진동과 열적 플러터에 대하여 연구하였다. 복합재료 얇은 벽보는 회전관성과 1차, 2차 와핑, 전단변형의 비고전적 요소를 포함한다. CUS구조물로 모델링한 복합재료 얇은 벽보의 열 진동 특성은 적층 순서와 섬유강화복합재료의 방향특성인자로부터 기인된 종방향 굽힘과 횡방향 굽힘의 언성과 관련하여 연구되었다. 수치 해석적인 방법으로 열적 플러터의 안정성 영역의경계값을 구하였으며, 태양 열 플럭스의 입사각, 감쇠계수, 섬유각의 변화에 의한 보의 변위를 구하였다. 주 구조물에 압전소자를 부착하여, 감지기와 작동기로 사용하여 제어해석을 수행하였다.