• Composites Research
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• 제23권6호
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• pp.19-25
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• 2010

본 논문은 유리섬유/에폭시 4-매 주자직 적층 복합재와 PVC 폼 코어로 제작된 철도차량용 복합재 대차프레임의 금속재 체결부 볼트 위치 최적화 연구에 대해 서술했다. 최적화 해석은 APDL(Ansys Parameter Design Language)을 이용한 서브모델링 기법을 적용하였으며 부분문제 근사방법에 의한 최적화를 수행하였다. 이때, 최적화 해석에 적용된 서브모델링 기법은 관심영역을 포함한 부분모델에 대한 계산을 재수행 함으로써 해석에 소요되는 시간을 절약하고 상세한 결과를 도출 할 수 있다. 복합재 대차프레임의 구조해석은 JIS E 4207에 의거하여 수행하였다. 서브모델링 기법을 적용한 복합재 대차프레임의 최적화 해석은 전체모델에 대한 결과에 비해 요소망 밀도의 조절을 통한 해석시간 절약과 상세한 결과를 얻을 수 있으며, 또한 볼트위치의 최적화로 인해 보다 낮은 Von-Mises 응력값이 나타남을 확인하였다.

• 대한기계학회논문집
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• 제18권12호
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• pp.3219-3226
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• 1994

A model is constructed to evaluate the stress intensity factors for a center crack subjected to polynomial anti-symmetric loading in a layered material. A Fredholm integral equation is derived by Fourier integral transform method. The integral equation is numerically analyzed to evaluate the effects of the ratios of shear modulus, Poisson's ratio and crack length to layer thickness as well as the number of layers on the stress intensity factor. The stress intensity factors are approached to constant values as the number of layers increase and decrease as the polynomial power of the loading increase. In case of the E-glass/Epoxy composite, dimensionless stress intensity factor is affected by cracked-resin layer thickness.

• Coupled systems mechanics
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• 제10권6호
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• pp.545-560
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• 2021

An in situ experiment imaged via X-ray computed tomography was performed on a continuous glass fiber mat reinforced epoxy resin composite. The investigated dogbone specimen was subjected to uniaxial cyclic tension. The reconstructed scans (i.e., gray level volumes) were registered via Digital Volume Correlation. The calculated maximum principal strain fields and correlation residual maps exhibited strain localization areas within the material bulk, thus indicating damage inception and growth toward the specimen surface. Strained bands and areas of elevated correlation residuals were mainly concentrated in the narrowest gauge section of the investigated specimen, as well as on the specimen ligament edges. Gray level residuals were laid over the corresponding mesostructure to highlight and characterize damage development within the material bulk.

• Composites Research
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• 제22권5호
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• pp.1-7
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• 2009

WR580/NF4000 유리섬유 에폭시 면재를 갖는 알루미늄 하니컴 샌드위치 복합재가 적용된 자동무인경전철 차체 구조물은 구조 시험과 유한요소 해석에 의해 평가되었다. 구조 시험은 JIS E 7105 규정에 따라 수행되었다. 차체 구조물의 추조 안전성은 다이얼 게이지와 가속도 센서를 통해 얻어진 처짐 및 고유진동수 결과에 의해 평가되었다. 그리고 제안된 유한요소 모델은 구조 시험 결과와 비교 되었으며, 유한요소 해석은 구조 시험과 잘 일치함을 보였다. 또한, 차제 구조물의 강성을 높이기 위해 언더프레임에 보강재가 적용된 모델은 설계단계에서 제안되었다. 보강된 언더프레임 모델을 갖는 복합재 차체 구조물은 구조 강성이 약 44%가 향상되었다.

• 대한기계학회논문집A
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• 제20권11호
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• pp.3433-3440
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• 1996

This paper was investigation of the stres corrosion cracking(SCC) mechanism and the properties of corrosion fracture surface of glass fiber reinforced plastics(GFRP) produced by hand lay up(HLU) method in synthetic sea water. Test material is GFRP, that was used vinylester type epoxy acrylate resin and an unsaturated polyester as the matrix and the chopped strand mat(CSM) type E-glss fiber as the reinforcement. The slow strain rate test(SSRT) was performed on dry, wet and saturated wet specimens in sea water. Here the pH concentration of synthetic sea water was 8.2 and the strain rate is 1 x $10^{-6}$($sec^{-1}$) and test temperature ranges varied from $-60^{\circ}C$ to $80^{\circ}C$. It could be confirmed the fact that wet specimens tested at a particular test temperature ranges were appeared the eviences of SCC such as con-planar, mirror and hackle zone. Moreover, SCC of GFRP in sea water was characterised by falt fracture surfaces with only small amounts of fiber pull-out, in partial.

• 대한기계학회논문집A
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• 제31권3호
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• pp.295-303
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• 2007

Degradation behaviors of filament-winded composites have been evaluated under the accelerated environmental test of high temperature, water immersion and thermal impact conditions. Two kinds of laminated composites coated by an urethane resin have been used: carbon-fiber reinforced epoxy(T700/Epon-826, CFRP) and glass-fiber reinforced phenolic (E-glass/phenolic, GFRP). For tensile strength of $0^{\circ}$ composites, CFRP showed little degradation while GFRP did high reduction by 25% under the influence of high temperature and water However for water-immersed $90^{\circ}$ composites tensile strength of both CFRP and GFRP showed high reduction. Bending strength and modulus of $90^{\circ}$ composites were largely reduced in water-immersion as well as high temperature environment. Urethane coating on the composite surface improved the bending properties by 20%, however hardly showed such improvement for water-immersed $90^{\circ}$ composites. In case of shear strength and modulus, both CFRP and GFRP showed high reduction by water-Immersion test but did a slight increase by high temperature and thermal impact conditions.

• 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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• 제57권1호
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• pp.105-126
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• 2016

In the present study, modelling and vibration control of axially moving laminated Carbon nanotubes/fiber/polymer composite (CNTFPC) plate under initial tension are investigated. Orthotropic visco-Pasternak foundation is developed to consider the influences of orthotropy angle, damping coefficient, normal and shear modulus. The governing equations of the laminated CNTFPC plates are derived based on new form of first-order shear deformation plate theory (FSDT) which is simpler than the conventional one due to reducing the number of unknowns and governing equations, and significantly, it does not require a shear correction factor. Halpin-Tsai model is utilized to evaluate the material properties of two-phase composite consist of uniformly distributed and randomly oriented CNTs through the epoxy resin matrix. Afterwards, the structural properties of CNT reinforced polymer matrix which is assumed as a new matrix and then reinforced with E-Glass fiber are calculated by fiber micromechanics approach. Employing Hamilton's principle, the equations of motion are obtained and solved by Hybrid analytical numerical method. Results indicate that the critical speed of moving laminated CNTFPC plate can be improved by adding appropriate values of CNTs. These findings can be used in design and manufacturing of marine vessels and aircrafts.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.933-937
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• 2002

The fiber reinforced composite material is widely used in the multi-industrial field where the weight reduction of the infrastructure is demanded because of their high specific modulus and specific strength. Pressure vessels using this composite material in comparison with conventional metal vessels can be applied in the field where lightweight and the high pressure are demanded from the defense and aerospace industry to rocket motor case due to the merits which are energy cutdown the weight reduction and decrease of explosive damage preceding to the sudden explosion which is generated by the pressure leakage condition). In this paper, for nonlinear finite element analysis of E-glass/epoxy filament winding composite pressure vessel receiving an internal pressure, the standard interpretation model is developed by using the ANSYS, general commercial software, which is verified as the accuracy and useful characteristic of the solution based on Auto LISP and ANSYS APDL. Both the preprocessor for doing exclusive analysis of filament winding composite pressure vessel and postprocessor that simplifies result of analysis have been developed to help the design engineers.

• Journal of the Korean Wood Science and Technology
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• 제27권2호
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• pp.15-22
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• 1999

진동 충격음 흡수성능을 지니는 샌드위치구조 목질 복합재료 제조용 폴리머는 넓은 온도범위(또는 주파수 범위)에서 높은 손실계수를 지니면서, 동시에 $5{\times}10^7\sim-10^9\;dyne/cm^2$의 탄성율을 지녀야 한다. 본실험에서는 이러한 점탄성 거동율 나타내는 고분자재료의 제조를 목적으로 에폭시 수지/아크릴 수지 상호침투망목고분자(IPNs)를 동시망목형성법으로 합성하였다. 고분자의 동적 점탄성은 Rheovibron을 사용하여 110Hz에서 측정하였으며, 복합체의 손실계수 및 동탄성 계수는 Rheovibron을 개조한 양단지지 강제 휨 진동법으로 주파수 110Hz에서 측정하였다. 동력학적 측정 결과, 손실탄성율의 최대값 온도 및 손실계수의 최대값 온도가 이동하고, 유리전이 영역이 확대되어, 이 IPNs계는 부분 상용계임을 알 수 있었다. 특히, 70/30 및 50/50 조성의 Epikote871/P(n-BMA) IPNs는 넓은 온도 범위에서 비교적 높은 손실계수 및 적당한 탄성율을 나타냈다. 또한 이를 적층한 목질 복합체는 넓은 온도 범위에서 비교적 높은 진동흡수 계수를 나타냈다.