• The magazine of the Korean Society for Advanced Composite Structures
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• v.6 no.1
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• pp.10-15
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• 2015

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.04a
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• pp.217-220
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• 1999

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.04a
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• pp.230-233
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• 1999

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.5199-5206
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• 2010

In this paper, we investigate the buckling analysis of laminated composite plates, using a improved assumed natural strain shell element. In order to overcome membrane and shear locking phenomena, the assumed natural strain method is used. The eigenvalues of the laminated composite plates are calculated by varying the width-thickness ratio and angle of fiber. To improve an shell element for buckling analysis, the new combination of sampling points for assumed natural strain method was applied and the refined first-order shear deformation theory which allows the shear deformation without shear correction factor. In order to validate the present solutions, the reference solutions are used and discussed. The results of laminated composite plates under the in-plane shear loading may be the benchmark test for the buckling analysis.

• Composites Research
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• v.19 no.2
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• pp.20-27
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• 2006

The hybrid composite materials with non-woven tissue (NWT) was developed to improve the mechanical properties of conventional FRP composite materials. The hybrid prepreg with NWT consists of FRP prepreg and NWT prepreg. The NWT prepreg consists of NWT and polymer resin. The NWT has short fibers, discretely distributed with in-plane random orientation fibers. The purposes of this study of hybrid prepreg with NWT are (i) to increase the interlaminar properties(the fracture toughness and strength), (ii) to improve the mechanical properties and reliability, while maintaining a low cost, (iii) to introduce a tough and strong interlayer at critical positions to be required of strength in the laminate. To accomplish the above purposes, a production technique to decrease voids in NWT layers was proposed in this paper. The interlaminar failure characteristics of laminated composite materials was tremendously improved by hybrid concept with NWT.

• Journal of Korean Society of Steel Construction
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• v.10 no.3 s.36
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• pp.451-461
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• 1998

The solution of anisotropic plate via the classical methods is limited to relatively load and boundary conditions. If these conditions are more complex, the analysis becomes increasingly tedious and even impossible. For many plate problems of considerable practical interest, analytic solutions to the governing differential equations cannot be found. Among the numerical techniques presently available, the finite difference method and the finite element method are powerful numerical methods. The objective of this paper is to compare with each numerical methods for the buckling load and modes of anisotropic composite laminated plates considering shear deformation. In applying numerical methods to solve differential equations of anisotropic plates, this study uses the finite difference method and the finite element method. In determining the eigenvalue by Finite Difference Method, this paper represent good convergence compared with Finite Element Method. Several numerical examples and buckling modes show the effectiveness of various numerical methods and they will give a guides in deciding minimum buckling load and various mode shapes.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.3
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• pp.723-734
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• 1991

본 연구에서는 투사체의 충격으로 인해 복합재에 발생하는 손상을 해석하기 위해 우선 이와 관련이 있는 손상에너지를 구할 수 있도록 동적 유한요소 프로그램을 개발하는데 있으며, 이렇게 구한 결과들을 Husman의 실험결과와 비교함으로써 본 논문 의 유한요소 프로그램이 적층복합보에 충격으로 인하여 전달되는 총에너지와 손상에너 지를 구하는데 타당한 것인가를 검토하고 이 프로그램을 이용하여 다음과 같은 것들을 해석하였다.

• Journal of Korean Society of Steel Construction
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• v.14 no.1
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• pp.23-29
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• 2002

Many of the bridge systems, including the girders and cross-beams, and concrete decks behave as the special orthotropic plates. Such systems with boundary conditions other than Navier or Levy solution types, or with irregular cross sections, analytical solution is very difficult to obtain. Numerical method for eigenvalue problems are also very much involved in seeking such a solution. A method of calculating the natural frequency corresponding to the first mode of vibration of beam and tower structures with irregular cross-sections was developed and reported by Kim in 1974. Recently, this method was extended to two dimensional problems including composite laminates, and has been applied to composite plates with shear deformation effects. In this paper, application of this method to the specially orthotropic laminated plates with various boundary condition is accomplished and the result of analysis is presented.

• Journal of the KSME
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• v.29 no.3
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• pp.231-243
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• 1989

복합재료의 탄성 문제를 정리하면 다음과 같다. 복합재료와 등방성 재료의 탄성학적 차이는 재료의 탄성계수에 기인하며 이것은 각각 다른 형태의 응력-변형률관계를 갖게 한다. 한편 응 력-변형률 관계식을 제외한 탄성학의 지배방정식은 재료의 종류에 관계없이 성립한다. 복합적 층판의 Stiffness와 응력 등은 Lamination 이론을 사용하여 구할 수 있다. 판이론은 평형식을 z방향으로 적분한 식, 즉 합력(resultant force)와 모멘트로 나타낸 평형식을 사용하는데 이 때 처짐 방정식을 구하기 위해 합력. 모멘트-곡률. 변형률 관계식을 이용하는데 이 관계식이 복합 재료와 등방성재료가 상이하다. 결과로 복합재료는 커플링 효과를 갖게 되며, 복합적층판을 대 칭으로 쌓으면 이 효과를 상쇄시킬 수 있다. 복합적층 보의 이론은 유효 굽힘 계수를 도입하면 등방체 보 이론을 사용하여 보의 처짐을 해석할 수 있다. 복합적층 보의 경우 굽힘 응력의 최 대치는 등방체와는 달리 보의 표면에서만 일어나지 않고 내부에서도 일어날 수 있다.

• Composites Research
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• v.18 no.6
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• pp.1-8
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• 2005

The fiber-reinforced composite materials have been advanced for various applications because of their excellent mechanical and electromagnetic properties. On their manufacturing processes, however, thermo-curing inherently produces the undesired thermal deformation mainly from temperature drop from the process temperature to the room temperature, so called spring-back. The spring-back must be understood especially in the hybrid composites in order to design and fabricate desired shape. In this research, (glass fiber / epoxy) + (carbon fiber / epoxy) unsymmetric hybrid composites were fabricated under various conditions such as cure cycle, laminate thickness, stacking sequence and curing sequence. Coupons were made and spring-back were measured using coordinate measuring machine (CMM). Using the Classical Lamination Theory (CLT) and finite element analysis (ANSYS), the behavior of spring-back were predicted and compared with the experimental data. The results from CLT and FEA agreed well with the experimental data. Although, the spring-back could be reduced by lowering curing temperature, at any case, the spring-back could not be removed completely.