• Composites Research
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• v.30 no.2
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• pp.149-157
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• 2017

In this paper, fracture behavior of laminated composites with notch was studied by cohesive zone modeling approach. The numerical modeling proceeded by first generating 3 dimensional solid element meshes for notched laminated composite coupon configurations. Then cohesive elements representing failure modes of fiber fracture, matrix cracking and delamination were inserted between bulk elements in all regions where the corresponding failures were likely to occur. Next, progressive failure analyses were performed simulating uniaxial tensile tests. The numerical results were compared to those by experiment available in the literature for verification of the analysis approach. Finally, notched laminated composite configurations with selected stacking sequences were analyzed and the failure behavior was carefully examined focusing on the failure initiation and progression and the dominating failure modes.

• 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.

• Composites Research
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• v.20 no.6
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• pp.15-20
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• 2007

In this work, the structural response of thin-walled, composite beams with built-in twist angles is analyzed using a mixed beam approach. The analytical model includes the effects of elastic couplings, shell wall thickness, and torsion warping. Reissner's semi-complimentary energy functional is used to describe the beam theory and also to deal with the mixed-nature in the beam kinematics. The bending and torsion related warpings introduced by the non-zero pretwist angles are derived in closed-form through the proposed beam formulation. The theory is validated with available literature and detailed finite element analysis results for rectangular solid section beams with elastic couplings. Very good correlation has been obtained for the cases considered.

• Composites Research
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• v.23 no.6
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• pp.7-13
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• 2010

Type3 cylinder is a composite pressure vessel fully over-wrapped with carbon/epoxy composite layers over an aluminum liner, which is the most ideal and safe high pressure gas container for CNG vehicles due to the lightweight and the leakage-before-burst characteristics. During service in CNG vehicle, if a fiber cut damage occurs in outer composite layers, it can degrade structural performance, reducing cycling life from the original design life. In this study, finite element modeling and analysis technique for the composite cylinder with fiber-cut crack damage is presented. Because FE analysis of type3 cylinder is path dependant due to plastic deformation of aluminum liner in autofrettage process, method to introduce a crack into FE model affect analysis result. A crack should be introduced after autofrettage in analysis step considering real circumstances where crack occurs during usage in service. For realistic simulation of this situation, FE modeling and analysis technique introducing a crack in the middle of analysis step is presented and the results are compared with usual FE analysis which has initial crack in the model from the beginning of analysis. Proposed analysis technique can be used effectively in the evaluation of influence of damage on composite layers of type3 cylinder and establish inspection criteria of composite cylinder in service.

• Composites Research
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• v.29 no.6
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• pp.347-352
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• 2016

This work presents the free vibration characteristics of laminated composite corrugated rectangular plates using the analytical method. Because it is very difficult to determine its mechanical behavior of 3-dimensional corrugated structures analytically, the equivalent homogenization model is adapted to investigate the overall mechanical behavior of corrugated structures. The corrugated element can be homogenized as an orthotropic material. Both the effective extensional and flexural stiffness of this homogenized equivalent orthotropic material are considered in the analysis. The present analytical results are validated by those obtained from 3D finite element analysis based on shell elements. The natural frequencies and global vibration mode shapes obtained from present analytical and finite element analysis are presented. Some numerical results are presented to check the effect of the geometric properties.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.5-8
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• 2001

진동의 이해를 위한 교육적 목적을 가지고서 복합재료 평판의 진동현상을 가시화하였다. 구조 진동의 특성으로 인해 나타나는 진동 모드의 노달 라인을 가시화할 수 있도록 하였다. 구조물의 가진을 위해 복합재료 평판의 모서리를 마찰 시킴으로써 전체 구조물의 진동을 유도하였다. 제작된 복합재료 평판에 대한 수치해석 결과와 실험 결과를 비교하였다.

• Composites Research
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• v.29 no.6
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• pp.321-327
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• 2016

In this study, tests and finite element analyses were performed regarding compression after impact strength for laminated composite structures of unidirectional carbon fiber reinforced plastic widely used in structural materials. Two lay-up sequences of composite laminates were selected as test specimens and four impact energy conditions were applied respectively. Impact and compressive strength tests were conducted in accordance with ASTM standards. Impact damages in test specimens were analyzed by using non-destructive inspection method of C-Scan, and compression after impact strengths were calculated with compressive test results. Progressive failure analysis method that can progressively simulate damages and fractures of fiber/matrix/lamina/laminate level was used for impact and compressive strength analyses. All analysis results including contact force, deflection, impact damages, compressive strengths, etc. were compared to test results, and the validity of analysis method was verified.

• Journal of the Society of Disaster Information
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• v.17 no.4
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• pp.839-847
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• 2021

Purpose: This study investigates mechanical behavior of functionally graded (FG) carbon nanotube-reinforced composite (CNTRC) plate in flexure. Isogeometric analysis (IGA) method coupled with shear deformable theory of higher-order (HSDT) to analyze the nonlinear bending response is presented. Method: Shear deformable plate theory into which a polynomial shear shape function and the von Karman type geometric nonlinearity are incorporated is used to derive the nonlinear equations of equilibrium for FG-CNTRC plate in bending. The modified Newton-Raphson iteration is adopted to solve the system equations. Result: The dispersion pattern of carbon nanotubes, plate geometric parameter and boundary condition have significant effects on the nonlinear flexural behavior of FG-CNTRC plate. Conclusion: The proposed IGA method coupled with the HSDT can successfully predict the flexural behavior of FG-CNTRC plate.

• 전기의세계
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• v.35 no.9
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• pp.611-619
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• 1986

전기기기의 해석법에는 첫째로 전기적 등가회로를 구성하여 이를 푸는 회로해석법과, 둘째로 현상을 지배하는 편미분방정식 또는 적분방정식을 적당한 가정하에서 푸는 수치해석법의 두가지가 있다. 그러나 회로해석법의 경우에는 회로망의 구성과 회로정수의 결정이 경험이나 직관에 따르게 되는등 여러가지 이유로 인해 앞으로의 발전을 기대하기가 곤란하다. 한편, 수치해석법의 경우에는 수치계산과정에서 반드시 오차가 수반되므로, 하나의 해석법만으로는 완전한 해석이 곤란하게 된다. 따라서 이 경우에는 문제의 특성에 따라 최적의 결과를 얻을 수 있는 복합적인 해석법이 선택사용되며, 근년의 전자계산기의 발달에 힘입어 전기기기의 해석에 광범위하게 이용되고 있다. 이러한 관점에서 본고에서는 전기기기의 해석에 사용되는 여러가지 수치해석법을 간단히 소개하고, 그중 최선의 방법으로서 가장 널리 연구활용되고 있는 유한요소법에 의한 각종 전기기기의 해석법에 대해 기술하기로 한다.

• Aerospace Engineering and Technology
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• v.2 no.1
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• pp.213-222
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• 2003

Some analytical methods to analyze low-velocity impact force history of composite laminated structures used in aerospace vehicles are reviewed. A classical method used at initial research of low-velocity impact problem in 1980s was reviewed on its physical meaning, and the approximate method assuming the shape of impact force history as a sinusoidal wave was reviewed. A parametric study on contact constant and exponent in contact law was performed in order to analyze an effect on impact force history, and finally its was understood that impact force history could be analyzed accurately even though the linearized contact law was used. Also, in this paper it was shown that impact problem could be analyzed simply and easily using a commercial finite element code.