• Title, Summary, Keyword: Layup sequences

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Nonlinear Dynamic Behaviors of Laminated Composite Structures Containing Central Cutouts (중앙개구부를 갖는 복합신소재 적층 구조의 비선형 동적 거동)

  • Ji, Hyo-Seon;Lee, Sang-Youl
    • Journal of Korean Society of Steel Construction
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    • v.23 no.5
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    • pp.607-614
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    • 2011
  • This study deals with thegeometrical nonlinear dynamic behavior of laminated plates made of advanced composite materials (ACMs), which contain central cutouts. Based on the first-order shear deformation plate theory (FSDT), the Newmark method and Newton-Raphson iteration wereused for the nonlinear dynamic solution. The effects of the cutout sizes and lay-up sequences on the nonlinear dynamic response for various parameters werestudied using a nonlinear dynamic finite element program that was developed for this study. The several numerical results agreed well with those reported by other investigators for square composite plates with or without central cutouts, and the new results reported in this paper showed significant interactions between the cutout and the layup sequence in the laminate. Key observation points are discussed and a brief design guide for laminates with central cutouts is given.

Nondestructive Defect Detection in Two-dimensional Anisotropic Composite Elastic Bodies Using the Boundary Element Method (경계 요소법을 이용한 2차원 비등방성 복합재료 탄성체의 비파괴 결함 추정)

  • 이상열
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.17 no.1
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    • pp.39-47
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    • 2004
  • In this paper, the defects of two-dimensional anisotropic elastic bodies are identified by using the boundary element method. The use of numerical models that contain only boundary integral terns reduces the dimensionality of the problem by one. This advantage is particularly important in problems such as crack mechanics. Avoiding domain meshing is also particularly advantageous in the solution of inverse problems since it overcomes mesh perturbations and simplifies the procedure. In this paper, nondestructive approaches for the existing isotropic materials are extended to analyze the elastic bodies made of anisotropic materials such as composites. After verifying that the proposing boundary element model is in good agreement with numerical results reported by other investigators, the effect of noise in the measurements on the identifiability is studied with respect to different design parameters of layered composites. Sample studies are carried out for various layup configurations and loading conditions. The effects of the layup sequences in detecting flaw of composites is explored in this paper.

Deflection Analysis of Laminated Composite Cylindrical Shell Structures Based on Micro-Mechanics (마이크로 역학기반 GFRP 원통형 적층 쉘 구조의 변위 해석)

  • Kim, Gyu-Dong;Lee, Sang-Youl
    • Journal of the Korean Society for Advanced Composite Structures
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    • v.4 no.4
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    • pp.15-21
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    • 2013
  • This study carried out finite element deflection analysis of cylindrical shell structures made of composite materials, which is based on the micro-mechanical approach for different fiber-volume fractions. The finite element (FE) models for composite structures using multi-scale approaches described in this paper is attractive not only because it shows excellent accuracy in analysis but also it shows the effect of the material combination. New results reported in this paper are focused on the significant effects of the fiber-volume fraction for various parameters, such as fiber angles, layup sequences, and length-thickness ratios. It may be concluded from this study that the combination effect of fiber and matrix, largely governing the dynamic characteristics of composite shell structures, should not be neglected and thus the optimal combination could be used to design such civil structures for better dynamic performance.

Structural Analysis and Design of Artificial Hip Joint by Using Finite Element Method (유한요소법을 이용한 인공 고관절의 역학적 거동 해석 및 설계)

  • 정재연;황운봉;하성규
    • Composites Research
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    • v.12 no.5
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    • pp.98-109
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    • 1999
  • An investigation has been performed to develop a nonlinear finire element method for the analysis of the long-term behavior of an artificial hip joint. The three dimensional multi-layered brick element is used to analyze the design performances of hip prodtheses with various materials and the thick laminated composite hip prostheses with various layup sequences. The used element can accommodate the varying material properties of the element and allow the ply-drop-off along the eleement edge. The nonlinear finite element analysis program has been verified by the comparison with the exact solution of the bean problem subjected to uniaxial loading. By using the program, the density changes and strength ratios of artificial hip joint are calculated according to the hip prosthesis materials and the layers of composite hip prosthesis. The numerical results are easily applied to evaluate design performances of a hip prosthesis, and decrease the difficulty and time of hip prosthesis design.

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Free Vibration Analysis based on HSDT of Laminated Composite Plate Structures Using Multi-scale Approach (멀티 스케일 접근 방법에 의한 복합소재 적층 판구조의 HSDT 기반 고유진동 해석)

  • Lee, Sang-Youl
    • Journal of The Korean Society of Civil Engineers
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    • v.34 no.1
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    • pp.61-71
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    • 2014
  • This study carried out finite element vibration analysis of composite plate structures for construction using multi-scale approaches, which is based on the higher-order theory. The finite element (FE) models for composite structures using multi-scale approaches described in this paper is attractive not only because it shows excellent accuracy in analysis but also it shows the effect of the material combination. The FE model is used for studying free vibrations of laminated composite plates for various fiber-volume fractions. In particular, new results reported in this paper are focused on the significant effects of the fiber-volume fraction for various parameters, such as fiber angles, layup sequences, and length-thickness ratios. It may be concluded from this study that the combination effect of fiber and matrix, largely governing the dynamic characteristics of composite structures, should not be neglected and thus the optimal combination could be used to design such civil structures for better dynamic performance.

Natural Frequency Characteristics of GFRP Pole Structures for Civil Structures with Different Fiber-Volume Fraction (모재-섬유 함침 비율에 따른 건설용 GFRP 기둥구조의 고유진동 특성)

  • Lee, Sang-Youl
    • Composites Research
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    • v.27 no.2
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    • pp.66-71
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    • 2014
  • This study carried out finite element vibration analysis of pole structures made of GFRP, which is based on the micro-mechanical approach for different fiber-volume fractions. The finite element (FE) models for composite structures using multi-scale approaches described in this paper is attractive not only because it shows excellent accuracy in analysis but also it shows the effect of the material combination. The FE model is used for studying free vibrations of laminated composite poles for various fiber-volume fractions. In particular, new results reported in this paper are focused on the significant effects of the fiber-volume fraction for various parameters, such as fiber angles, layup sequences, and length-thickness ratios. It may be concluded from this study that the combination effect of fiber and matrix, largely governing the dynamic characteristics of composite structures, should not be neglected and thus the optimal combination could be used to design such civil structures for better dynamic performance.

Prediction of Fatigue life of Composite Laminates using Micromechanics of Failure (미시역학적 파손이론을 이용한 복합재 적층판의 피로수명 예측)

  • Jin, Kyo-Kook;Ha, Sung-Kyu;Kim, Jae-Hyuk;Han, Hoon-Hee
    • Composites Research
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    • v.24 no.1
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    • pp.10-16
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    • 2011
  • Many tests are required to predict the fatigue life of composite laminates made of various materials and having different layup sequences. Aiming at reducing the number of tests, a methodology was presented in this paper to predict fatigue life of composite laminates based on fatigue life prediction of constituents, i.e. the fiber, matrix and interface, using micromechanics of failure. For matrix, the equivalent stress model which is generally used for isotropic materials was employed to take care of multi-axial fatigue loading. For fiber, a maximum stress model considering only stress along fiber direction was used. The critical plane model was introduced for the interface of the fiber and matrix, but fatigue life prediction was ignored for the interface since the interface fatigue strength was presumed high enough. The modified Goodman equation was utilized to take into account the mean stress effect. To check the validity of the theory, the fatigue life of three different GFRP laminates, UDT[$90^{\circ}2$], BX[${\pm}45^{\circ}$]S and TX[$0^{\circ}/{\pm}45^{\circ}$]S was examined experimentally. The comparison between predictions and test measurements showed good agreement.