• 한국전산구조공학회논문집
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• 제21권1호
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• pp.51-58
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• 2008

본 연구에서는 입자강화 복합재료(particle-reinforced composites)의 거동을 예측하기 위하여 Lee and Pyo(2007)에 의해 제안된 계면손상을 고려한 복합재료의 미세역학 탄성모델과 Karihaloo and Fu(1989)의 미세균열 생성모델을 결합하여, 보강입자의 계면손상(imperfect interface)과 기지 내 미세균열을 고려하여 탄성구성모델(constitutive model)의 거동해석을 수행하였다. 제안된 탄성구성모델의 적용성 검증과 주요손상변수가 거동예측에 미치는 영향을 알아보기 위해 일축 하중 하에서의 응력-변형률 관계를 수치적으로 나타내었다. 또한, 기존의 관련 실험결과와 본 해석결과와의 비교를 통하여 제안된 모델의 정확도를 검증하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1997년도 가을 학술발표회 논문집
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• pp.119-125
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• 1997

The finite element analysis of plate and shell structures has been one of the major research interests for many years because of the technological importance of such structures. Quite often these structures are constructed by laminated composites. This is due to the high specific stiffness and strength of composite structures. The main objective of this paper is to extend the use of an improved degenerated shell element to the large displacement analysis of plates and shells with laminated composites. The total Lagrangian approach has been chosen for the definition of the deformation and the solution to the nonlinear equilibrium equations is obtained by the Newton-Raphson method.

• Composites Research
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• 제30권1호
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• pp.26-34
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• 2017

본 연구에서는 직물섬유 복합재의 열전도를 구하는데 있어 기존의 연구보다 개선된 방법을 제시하고, 직물섬유의 기하학적 구조가 복합재의 열전도도 향상에 미치는 영향, 그리고 유전 알고리즘(Genetic algorithm)을 이용하여 복합재의 열전도도 향상을 위한 최적구조 설계에 관한 연구를 하였다. 직물섬유의 구조를 토우의 물결무늬와 너비 및 두께를 이용하여 구현하였고, 열전도도는 열전기유사법(Thermal-electrical analogy)을 이용하여 구하였다. 유전 알고리즘에서 염색체 문자열은 fill과 warp tow의 두께와 너비로 하였고 복합재의 열전도도를 향상 시키는 방향으로 목적함수를 정하였다. 연구결과 직물섬유 복합재의 열전도도를 예측을 위한 향상된 방법이 제시되었고, 섬유토우 사이의 간격(inter-tow gap)이 넓어 질수록 복합재의 열전도도가 감소하는 것으로 나타났다. 직물섬유 복합재의 구조 최적화에서는 이론적 수치해석 결과가 제시되었는데, 전체적으로 섬유토우(tow)의 축의 수직방향보다는 축 방향의 열전도도 성분이 복합재의 전체 열전도도 향상에 크게 기여를 하는 것으로 나타났다.

• Advanced Composite Materials
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• 제16권4호
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• pp.269-282
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• 2007

Fully biodegradable high strength composites or 'advanced green composites' were fabricated using yearly renewable soy protein based resins and high strength liquid crystalline cellulose fibers. For comparison, E-glass and aramid ($Kevlar^{(R)}$) fiber reinforced composites were also prepared using the same modified soy protein resins. The modification of soy protein included forming an interpenetrating network-like (IPN-like) resin with mechanical properties comparable to commonly used epoxy resins. The IPN-like soy protein based resin was further reinforced using nano-clay and microfibrillated cellulose. Fiber/resin interfacial shear strength was characterized using microbond method. Tensile and flexural properties of the composites were characterized as per ASTM standards. A comparison of the tensile and flexural properties of the high strength composites made using the three fibers is presented. The results suggest that these green composites have excellent mechanical properties and can be considered for use in primary structural applications. Although significant additional research is needed in this area, it is clear that advanced green composites will some day replace today's advanced composites made using petroleum based fibers and resins. At the end of their life, the fully sustainable 'advanced green composites' can be easily disposed of or composted without harming the environment, in fact, helping it.

• Structural Engineering and Mechanics
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• 제64권3호
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• pp.287-292
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• 2017

In the present research, an available flexural stiffness degradation model was modified and a new comprehensive model called "X-NFSD" was developed. The X-NFSD model is capable of predicting the flexural stiffness degradation of composite specimen at different states of stresses and at room temperature. The model was verified by means of different experimental data for chopped strand mat/epoxy composites under displacement controlled bending loading condition at different displacements and states of stresses. The obtained results provided by the present model are impressively in very good agreement with the experimental data and the mean value of error of 5.4% was achieved.

• 한국전산구조공학회논문집
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• 제25권1호
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• pp.65-71
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• 2012

본 논문에서는 수상/육상 착륙 환경에서 경항공기용 플로트의 구조적 안전성과 경량화 설계개선을 위하여 고유 진동수 및 정적 응력해석을 수행하였다. 경항공기용 플로트의 설계제원 및 형상도면을 기반으로 유한요소 모델링을 수행하였으며, 수상/육상 착륙 시점의 단순화된 하중조건을 플로트모델에 적용하였다. 먼저 알루미늄 플로트모델에 대하여 고유 진동수 및 응력해석 결과를 확인하였으며, 이를 기준으로 복합재료 적층판을 적용한 플로트모델의 구조적 안전성을 비교 검토하였다. 복합재료 플로트모델의 적층유형 및 두께 변화에 따른 무게감소와 파손지수 변화 등의 성능개선을 확인하였으며, 경량화 플로트설계에 적합한 적층유형을 제시하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.1103-1108
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• 2009

This paper describes the results of structural test and finite element analysis for rubber wheel-type Automatic Guideway Transit(AGT) made of aluminum honeycomb sandwich composites with WR580/NF4000 glass-fabric epoxy laminate face sheets. The static tests of vehicle structure were conducted according to JIS E7l05. These static tests have been done under vertical load, compressive load and 3-point support load. The structural integrity of AGT vehicle structure was evaluated by displacement, stress obtained from LVDT and strain gauges, and natural frequency. And finite element analysis using Ansys v11.0 was done to compare with the results of static test. The result showed that the results of structural integrity for static test were in an good agreement with these of finite element analysis.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.21-24
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• 2004

Structural performance of the seismic devices made by steel bar and high performance fiber reinforced cement composites(HPFRCCs) was experimentally observed. These dampers will be applied for reducing damage as well as seismic response. The advantages of the HPFRCCs damper is selective structural performance, strength, stiffness, and ductility by changing configuration, bar arrangements and type of materials used. The experimental results indicate that elemental ductility is much increased with decreasing damage when the HPFRCCs are applied to the damper. It means cementitious damper for structural control is available which has much merit in performance and cost.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.275-278
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• 2005

High performance fiber reinforced cement composites(HPFRCCs) is a class of high ductile fiber reinforced cementitious composites developed for applications in the sensitive construction industry. HPFRCCs has undergone major evolution in both materials development and the range of emerging applications. This paper is to evaluate structural strengthening performance of LRCF(Lightly reinforced concrete frame) using the HPFRCCs. The experimental results, as expected, show that the crack load, yield load, and limited load are superior for specimen with HPFRCCs infill wall due to crosslink effect of fibers in concrete.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 봄 학술발표회 논문집
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• pp.407-414
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• 2002

The knowledge of interaction of electromagnetic waves in composite structures is important for designing the shielding structure for antenna such as radome. Recently, radomes are constructed in the form of foam core sandwich structures that have many mechanical advantages such as high strength, long fatigue life, low density and adaptability to the intended function of structure. However, the propagation of electromagnetic waves is affected by high anisotropic permeability and loss tangent of the composite skin. In this study, the analytical model to understand the propagation of electromagnetic waves in the anisotropic composites and foam core sandwich structures with composite skins was proposed. Numerical analyses of unidirectional composites and foam core sandwich structure as a function of incident angle were performed. From the results of analysis, the general tendencies of transmittance of electromagnetic wave through composites and foam core sandwich structure were obtained.