• 한국추진공학회지
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• 제5권1호
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• pp.42-48
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• 2001

지난 20년 동안 인장하중과 굽힘 하중 상태에서 복합재료 적층판의 크기효과에 관한 많은 연구가 수행되었으며, 시편의 크기를 증가함에 따라 복합재 적층판의 강도가 저하되는 경향은 잘 알려져 있다. 그러나, 복합재 압축시험의 어려움으로 인해 압축하중 상태에서 시편의 파괴강도에 대한 크기효과에 관한 연구는 거의 수행되지 않았다. 본 연구에서는 홀을 갖는 복합재의 압축 강도에 대한 크기 효과를 고찰하기 위해 T300/924C, $>[45/-45/0/90]_{3S}$를 사용하였으며, 시편의 크기 변화를 위해 2차원면적 변화(시편의 폭 및 길이 변화)를 고려하는 평면 스케일링 방법을 사용하였다. 실험 결과는 유한폭을 가지는 평판에 대한 명확한 홀 크기 효과를 보였을 뿐만 아니라, 같은 a/W(홀 직경/시편 폭)를 갖는 시편에서도 크기 효과를 확인할 수 있었다. 반면에, 홀이 없는 시편은 명확한 강도 크기 효과를 보이지 않았다.

• Composites Research
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• 제20권5호
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• pp.56-63
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• 2007

복소퍼텐셜을 이용하여 타원공 또는 균열을 내재한 복합재 적층판구조 해석법을 고찰하였다. 복합재 적층판은 충격에 취약하며 이러한 충격손상은 타원공이나 균열형태의 노치로 모델화된 바 있다. 이와 같이 컷아웃부를 내재한 복잡한 형태의 복합재 적층판 해석에 유한요소해석법이 널리 사용되고 있으나 피로하중 하에서의 손상허용성 평가와 같이 손상진전에 따라 반복적으로 유한요소모델링을 수정하여 해석을 수행하여야 하는 경우 매우 번거로운 작업이 요구된다. 이러한 관점에서 복소퍼텐셜을 이용한 해석적 기법은 매우 간편하고 사용하기 손쉬운 기법이라고 할 수 있다. 이러한 해석법에 의한 계산결과를 유한요소해석 결과와 비교 분석함으로써 계산과정의 유효성과 용이성을 검증하였다.

• 대한기계학회논문집A
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• 제24권1호
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• pp.259-268
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• 2000

Because of their superior mechanical properties to isotropic materials, composite laminated plates are used for many structural applications that require high stiffness-to-weight and strength-to-weight ratios. Composite materials are always subject to a certain amount of scatter in their elastic moduli, but most analyses and designs with the materials are usually conducted by assuming that the material properties are fixed and have no uncertainties. In this paper, a convex modeling approach is introduced to take account of such uncertainties in elastic moduli. It is used with the finite element method to predict the onset of failures in composite laminated plates subject to in-plane loading. Numerical results show that failures begin at the smaller load when the uncertainties of elastic moduli considered and therefore, such uncertainties should be considered at the design stage for the safety and reliability of the structures.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.155-158
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• 2001

The layup optimization by genetic algorithm (GA) for the strength of laminated composites with free-edge is presented. For the calculation of interlaminar stresses of composite laminates with free edges, extended Kantorovich method is applied. In the formulation of GA, repair strategy is adopted for the satisfaction of given constraints. In order to consider the bounded uncertainty of material properties, convex modeling is used. Results of GA optimization with scattered properties are compared with those of optimization with nominal properties. The GA combined with convex modeling can work as a practical tool for light weight design of laminated composite structures since uncertainties are always encountered in composite materials.

• 국방과기술
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• 10호통권164호
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• pp.43-44
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• 1992

복합재 연소관과 노즐을 기계적 체결방법으로 결합하면 결합부위에서 재료의 불연속성과 기하학적 불연속성으로 인한 높은 응력집중이 발생해 구조적으로 매우 취약하게 됩니다. 복합재 연소관의 경우에는 내압을 받는 원통형 구조물이므로 기존의 평판에 대한 연구결과를 그대로 사용할수 없으므로, 이 글에서는 복합재 셀 구조물의 응력 및 파손 해석을 수행할수 있도록 1차전단변형 셀이론을 이용한 유한요소해석 프로그램을 개발하였습니다. 기계적체결부위의 모델링에 대해 검토하였으며 복합재료의 파손평가에 사용되는 여러가지 파손식을 적용해 비교하였습니다. 이 해석 방법을 이용해 복합재 연소관의 적층각, 볼트직경, 연소관의 끝단까지의 길이 등이 파손하중에 미치는 영향을 제시하였습니다

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.249-252
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• 2005

Prediction of damage caused by low-velocity impact in laminated composite plate is an important problem faced by designers using composites. Not only the inplane stresses but also the interlaminar normal and shear stresses playa role in estimating the damage caused. The work reported here is an effort in getting better predictions of damage in composite plate using DNS approach. In the DNS model, we discretize the composite plates through separate modeling of fiber and matrix for the local microscopic analysis. Through comparison with the homogenized model. In the view of microscopic mechanics with DNS model, interlaminar stress behaviors in the inside of composite materials is investigated and compared with the results of the homogenized model which has been used in the conventional approach of impact analysis.

• 대한기계학회논문집A
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• 제28권9호
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• pp.1337-1343
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• 2004

Shape optimization was performed to obtain a precise shape of cutouts including the internal shape of cutouts in a laminated composite plate by three dimensional modeling using solid element. Volume control of the growth-strain method was implemented and the distributed parameter chosen as Tsai-Hill fracture index for shape optimization. It makes Tsai-Hill failure index at each element uniform in laminated composites under the predetermined volume a designer requires. Shapes optimized by Tsai-Hill failure index were compared with those of the initial shapes for the various load conditions and cutouts. The following conclusions were obtained in this study; (1) It was found that growth-strain method was applied efficiently to shape optimization of three dimensional cutouts in a laminate composite, (2) The optimal shapes of the various load conditions and cutouts were obtained, (3) The maximum Tsai-Hill failure indices of the optimal shapes were remarkably reduced comparing with those of the initial shapes.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 추계학술대회
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• pp.277-282
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• 2003

The growth-strain method was applied to cutout optimization in laminated composite plates. Since the growth-strain method optimizes a shape by generating the bulk strain to make the distributed parameter uniform, the distributed parameter was chosen as Tsai-Hill value. In this study, of particular interest is to see whether the growth-strain method developed for shape optimization in isotropic media would work for laminated composite Plates. In volume control of the growth-strain method, it makes Tsai-Hill value at each element uniform in laminated composite plates under the predetermined volume. The shapes optimized by Tsai-Hill fracture index were compared with those of the initial shapes for the various load conditions and predetermined volumes of laminated composite plates. As a result, it was verified that volume control of the growth-strain method worked very well for cutout optimization in laminated composite plates.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
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• pp.69-73
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• 1999

This study discusses a non-contact optical technique, electronic speckle pattern interferometry(ESPI), that is well suited for in-plane and out-of-plane deformation measurement. AS4/PEEK[30/-30/90]s, composite laminate plate was analyzed by ESPI to determine the vibration characteristics with tensile loading and without it. vibration mode shapes are quantitatively compared with the result of numerical analysis. The experimental results agree well with those of numerical analysis. we found that when the composite laminate plate is under the tensile loading, vibration modes can be measured with high accuracy by ESPI.

• 한국전기전자재료학회논문지
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• 제13권1호
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• pp.39-46
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• 2000

An analysis of the free vibration for the metal-piezoceramic laminated thin plates is described. The purpose of this study is to develop a equivalent method for the free vibration analysis of metal-piezoce-ramic laminated thin plate which are not sysmmetric about the adhered layer and the piezoelectric effect. In order to confirm the validity of the vibration analysis, double Fourier sine series is used as a modal displacement function of a metal-piezoceramic laminated thin plate and applied to the free vibration analysis of the plate under various boundary conditions.