• Title, Summary, Keyword: 적층복합재

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Optimal Design of Laminated Composite Beams with Open Cross Section (복합 적층 개단면 보의 최적설계)

  • 배하록;홍순호;신영석
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.14 no.2
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    • pp.107-116
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    • 2001
  • 복합재 적층판은 중량에 비해 높은 강성과 강도가 요구되는 공학의 다양한 분야에서 매우 유용하다. 보강섬유 복합재의 공학적 활용이 활발해지고, 중량의 감소화가 설계의 중요한 목적이 됨으로써, 근래 복합재 구조물들의 최적화 설계의 중요성이 대두되고 있다. 그러나 복합재 적층 구조물 재료의 비등방성에 의해 해석과 설계가 매우 어렵다. 본 연구에서는 수치적 최적화 방법과 유한요소법을 이용하여 보강섬유 복합재의 최적설계를 하였다. 복합재 적층판으로 이루어진 개단면 보에 있어서 보강섬유의 다양한 적층방향에 대한 거동의 영향을 규명하였다.

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Three Dimensional Stress Analysis of Composite Laminates using Stress Functions and Interface Modeling (응력함수와 층간면 모델링을 이용한 복합재 적층판의 3차원 응력해석)

  • Kim, H.S.;Kim, J.Y.;Kim, J.G.
    • Journal of the Korea Society For Power System Engineering
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    • v.13 no.4
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    • pp.49-55
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    • 2009
  • 복합재 적층판의 자유단 근처에서 나타나는 층간 응력의 집중 현상을 층간면 효과를 고려해 해석하였다. 복합재 적층판 내부의 임의의 위치에서 3차원 평형방정식을 만족시키기 위해 렉니츠키 응력함수를 도입하였으며, 가상일의 원리를 이용하여 지배방정식을 유도하였다. 주어진 응력함수를 이용하여 구한 3차원 응력들은 복합재 적층판의 아래 위 면뿐만 아니라 자유단에서 하중자유조건을 잘 만족한다. 기하학적 불연속성 때문에 복합재 적층판의 자유단에서는 응력의 특이가 발생하지만, 층간면 효과를 고려하게 되면 층간응력의 집중현상을 정확하게 해석할 수 있다. 자유단에서 발생한 층간응력의 크기를 보면, 층간면 효과를 고려할 경우, 응력특이 효과가 많이 줄어드는 것을 관찰할 수 있다. 본 연구에서 주어진 층간면에서의 정확한 응력 해석은 복합재 적층판의 강도설계를 수행하는 초기 설계 툴로 사용할 수 있다.

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A Study on the Evaluation of the Failure for Carbody Structures made of Laminated Fiber-Reinforced Composite Materials Using Total Laminate Approach (전체 적층판 접근법을 이용한 섬유강화 적층 복합재 차체 구조물의 파손평가 연구)

  • 신광복;구동회
    • Composites Research
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    • v.17 no.1
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    • pp.18-28
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    • 2004
  • In order to evaluate the strength of carbody structures of railway rolling stock made of laminated fiber-reinforced composite materials, total laminate approach was introduced. Structural analyses were conducted to check the basic design of hybrid composite carbody structures of the Korean Tilting Train eXpress(TTX) with the service speed of 180km/h. The mechanical tests were also conducted to obtain strengths of composite laminates. The results show that all stress components of composite carbody structures are inside of failure envelopes and total laminate approach is recommended to predict the failure of hybrid composite carbody structures at the stage of the basic design.

Strength Optimization of Laminated Composite Patches Using Genetic Algorithm (유전 알고리듬을 이용한 복합재 적층 패치의 최적강도설계)

  • Lee, Jae-Hun;Cho, Maeng-Hyo;Kim, Heung-Soo
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.729-732
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    • 2010
  • 본 논문에서는 이산 변수 최적화에 적합한 유전 알고리듬을 이용하여 복합재 적층 패치의 최적강도설계를 수행하였다. 기저판(substrate)와 접착제(adhesive), 그리고 복합재 적층 패치로 이루어진 구조물에서 패치의 강도를 효율적으로 구하기 위해서 응력 함수 기반의 해석적 방법을 도입하였다. 면외 방향의 응력 함수를 가정하여 가상 공액일의 법칙(complementary virtual work principle)에 적용하였으며, 복합재 패치의 자유 경계조건으로부터 면내 방향의 응력함수를 결정하였다. 응력 함수를 통하여 구한 층간 응력 값은 자유 경계 효과를 잘 나타내었고, 이를 이용하여 패치의 강도 해석을 수행하였다. 강도 해석 시, 복합재 패치의 파괴 기준은 면내 응력들에 대해서는 최대 응력 척도를 사용하였으며, 층간 응력들에 대해서는 quadratic delamination 척도를 사용하였다. 유전 알고리듬을 이용한 최적강도설계 과정에서는 임의의 염색체가 주어진 적층 구속 조건을 만족할 수 있게 수정(repairing)하는 과정을 도입하였다. 또한 다수의 전역해(global optima)를 효과적으로 찾기 위해서 multiple elitism 기법을 도입하였다. 응력 함수 기반의 강도 해석방법과 유전 알고리듬과의 연계를 통한 복합재 적층 패치의 강도최적설계 기법은 패치 구조물의 해석 및 설계에 있어서 효율적인 도구로서 사용할 수 있을 것이라 사료된다.

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A Method to Predict the Open-Hole Tensile Strength of Composite Laminate (원공을 가지는 복합재 적층판의 인장강도 예측 기법)

  • Lee, Heun-Ju;Shin, In-Soo;Jeong, Mun-Gyu;Kweon, Jin-Hwe;Choi, Jin-Ho
    • Composites Research
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    • v.24 no.4
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    • pp.29-35
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    • 2011
  • The characteristic length method used to determine a laminate's strength generally requires the test for un-notched and notched laminates and finite element analysis together. In this paper, the methods used to predict the stress distribution and tensile characteristic length of open-hole laminates using the stress concentration factor and equivalent material properties are proposed. These methods do not require data on the failure load of open-hole laminates or finite element analysis. Once the stress and characteristic length have been determined, the failure load of the open-hole laminate can be calculated. The proposed method considers the effect of the material properties as a parameter and therefore can be applied to a variety of materials. The stress distribution is verified by comparing with a finite element analysis and test results. The predicted failure load shows a maximum deviation of 8% from the test results.

The Study on the Characteristics of Mode I Crack for Cross-ply Carbon/Epoxy Composite Laminates Based on Stress Fields (응력장을 이용한 직교적층 탄소섬유/에폭시 복합재 적층판의 모드 I 균열 특성 연구)

  • Kang, Min-Song;Jeon, Min-Hyeok;Kim, In-Gul;Woo, Kyeong-Sik
    • Composites Research
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    • v.32 no.6
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    • pp.327-334
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    • 2019
  • The delamination is a special mode of failure occurring in composite laminates. Several numerical studies with finite element analysis have been carried out on the delamination behavior of unidirectional composite laminates. On the other hand, the fracture for the multi-directional composite laminates may occur not only along the resin-fiber interface between plies known as interply or interlaminar fracture but also within a ply known as interyarn or intralaminar fracture accompanied by matrix cracking and fiber bridging. In addition, interlaminar and intralaminar cracks appear at irregular proportions and intralaminar cracks proceeded at arbitrary angle. The probabilistic analysis method for the prediction of crack growth behavior within a layer is more advantageous than the deterministic analysis method. In this paper, we analyze the crack path when the mode I load is applied to the cross-ply carbon/epoxy composite laminates and collect and analyze the probability data to be used as the basis of the probabilistic analysis in the future. Two criteria for the theoretical analysis of the crack growth direction were proposed by analyzing the stress field at the crack tip of orthotropic materials. Using the proposed method, the crack growth directions of the cross-ply carbon/epoxy laminates were analyzed qualitatively and quantitatively and compared with experimental results.

The Absorbed Energy of Carbon/Epoxy Composite Laminates Subjected to High-velocity impact in Considering the Loss of Projectile Mass (고속충격을 받는 Carbon/Epoxy 복합재 적층판의 충격체 질량손실을 고려한 흡수에너지 예측)

  • Cho, Hyun-Jun;Kim, In-Gul;Lee, Seokje;Kim, Young-A;Woo, Kyeongsik
    • Composites Research
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    • v.26 no.6
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    • pp.349-354
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    • 2013
  • In this paper, we conducted high velocity impact test for Carbon/Epoxy composite laminates and proposed advanced method for predicting the absorbed energy of composite laminates. During high-velocity impact test, we discovered loss of projectile mass macroscopically using high speed camera, thus we calculated the absorbed energy of composite laminates by taking loss of projectile mass into account. We proposed a model for predicting the absorbed energy of composite laminates subjected to high-velocity impact, the absorbed energy was classified into static energy and dynamic energy. The static energy was calculated by the quasi-static perforation equation that is related to the fiber breakage and static elastic energy. The dynamic energy can be divided by the kinetic energy of deformed specimen and fragment mass. Finally, the predicted absorbed energy considering loss of projectile mass was compared with experimental results.

Study on through the thickness stresses in the corner radius of a laminated composite structure (복합재 구조물의 모서리 곡면 부위에 대한 두께방향 응력 연구)

  • Kim, Sung Joon;Hwang, In Hee
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.41 no.8
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    • pp.665-672
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    • 2013
  • One of the major causes of stiffness and strength degradations in laminated composite structures is the delamination between composite layers. In most engineering applications, laminated composite structures have certain curvatures. If the curved composite structure is subjected to bending that tends to flatten the composite structures, through the thickness stresses can be generated in the thickness direction of the composites. Under normal operation open mode delamination could occur at the sites of peak interlaminar stress. This paper describes a technique to determine radial direction stress of a laminated composite structure using a curved beam. Stacking sequence effects of interlaminar stress were studied. The radial location and intensity of the open mode delamination stress were calculated and compared with the results obtained from the analytical solution and finite element method.

Reduction of Free Edge Peeling Stress in Composite Laminates under Bending Load (굽힘하중이 가해지는 복합재 평판 자유단에서의 박리응력 감소 연구)

  • Jung, Seok-Joo;Sung, Myung-Kyun;Kim, Heung Soo
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.28 no.5
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    • pp.497-502
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    • 2015
  • In this paper, a stress function-based approach was proposed to analyze the reduction of free-edge peeling stress in smart composite laminates using piezoelectric actuator under bending load. Electro-mechanically coupled governing equation was obtained by complimentary virtual work principle. The stress state was solved by the generalized eigenvalue procedure. The free-edge peeling stress of smart composite laminates was reduced by the piezoelectric actuation. The reduction rate of peeling stress in cross-ply composite laminate is larger than that in angle ply composite laminate.

High velocity Impact Analysis of Carbon/Epoxy Composite Laminates (탄소/에폭시 복합재 적층판의 고속충돌 관통해석)

  • Kim, Young-Ah;Woo, Kyeongsik;Yoo, Won-Young;Kim, In-Gul;Kim, Jong-Heon
    • Composites Research
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    • v.25 no.6
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    • pp.191-197
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    • 2012
  • In this paper, the penetration behavior of carbon/epoxy composite laminates subjected to high velocity projectile impact was studied by numerical simulation. The composite laminates made of carbon/epoxy with $[45/0/-45/90]_{ns}$ stacking sequence and the spherical steel impactor were three-dimensionally modeled. The ply numbers of 16 and 24 and the impact velocities in the range of 140-250 m/s were considered. The analysis was performed using an explicit finite element code LS-DYNA. The residual velocity and the amount of damage were predicted and compared to the experimental results.