• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.1
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• pp.37-44
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• 1999

비등방성으로 적층된 복합판 및 쉘구조물에서 온도와 습도의 급격한 변화는 구조물의 강도와 성능을 저하시키는 중요한 원인이 된다. 더욱이 하중에 의한 역학적 변위와 조합될 때에는 좌굴, 대변형 혹은 고응력 상태를 유발하게 된다. 본 연구에서는 이중 퓨리에급수를 이용하여 3차의 전단변형함수로 가정된 평형방정석을 전개하고 폭-두께비, 형상비의 변화 그리고 재료의 성질에 따른 결과에 대하여 고찰하였다.

• Journal of the Korean Society for Advanced Composite Structures
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• v.1 no.2
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• pp.44-50
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• 2010

The behaviour of Modular GFRP(Glass Fiber Reinforced Polymers) decks for use in deteriorated bridge decks replacement are investigated experimentally in this study. As for the performance evaluation of bridge decks, experimental studies on the 3 test specimens with 1/5 scale of full size were carried out. Three specimens were sandwich plates with box tube cores. The constituents of bridge decks were glass fiber preforms and epoxy resin. The experimental results of all the specimens were summarized for maximum strength, stiffness and deformation capacity. A finite element analyses were compared to verify validity of experimental results.

• Composites Research
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• v.24 no.5
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• pp.29-33
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• 2011

The application of high performance materials for the deck can represent a fair alternative to reduce the weight of the deck and improve the econimic efficiency of the bridge even if high performance materials are costly. In UHPC(Ultra High Performance Concrete) bridges, it is necessary to verify that exiting headed stud can be used to transfer longitudinal shear forces across the steel-concrete interface. In this paper, the push-out tests are performed to analisys the composite behavior between UHPC bridge deck and steel girder. The ultimate strength of test specimens is proportional to the diameter of headed studs in push-out test for static loading. Test results show that the shear strength of headed stud is improved for the case of normal concrete bridge decks.

• Composites Research
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• v.12 no.4
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• pp.25-32
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• 1999

A method of calculating the natural frequency corresponding to the first mode of vibration of beams and tower structures, with irregular cross sections and with arbitrary boundary conditions was developed and reported by Kim, D. H. in 1974. In this paper, the result of application of this method to the special orthotropic plates on elastic foundation with free boundaries is presented. Such plates represent the concrete highway slab and hybrid composite pavement on bridges. Any method may be used to obtain the deflection influence surfaces needed for this vibration analysis. Finite difference method is used for this purpose, in this paper. The influence of the modulus of the foundation and the aspect ratio of the plate on the natural frequency is thoroughly studied. The effect of neglecting the mass of the plates on the natural frequency, as the ratio of the point mass/masses to the plate mass increases, is also studied, in deep.

• Composites Research
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• v.12 no.1
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• pp.28-36
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• 1999

Thermal stress-induced failure in the free edge region of various thin carbon/epoxy composite laminates(1mm thick) has been investigated using the three-dimensional finite-element stress analysis, ultrasonic C-scan and microscopic observations. High thermal in-plane and interlaminar stresses were predicted in the interior layer near the free edge boundaries of the laminates. In the interior lamina, not in the skin lamina, of the thin laminates with lay-up of $[0_2/90_2]_s,\;[45_2/-45_0]_s,\;[0_2/60_2]_s$ treated by liquid $N_2$ immersion, many transverse matrix cracks took place due to thermal stress concentration, which agreed qualitatively with the above predictions.

• Composites Research
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• v.16 no.1
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• pp.50-57
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• 2003

Usually many researchers have used the modified Hertzian contact law or experimental static indentation law to analyze impact response of composite laminates subjected to the low-velocity impact. In this study, physical meaning of the method using the laws was investigated and the difference between the analytical results obtained using the laws was also investigated. Furthermore parametric study on contact constant and exponent in the contact law was performed. Finally it was shown that a linearized contact law can be well applied to low-velocity impact response analysis of composite laminates. If this concept is used, commercial finite element software can be used to solve impact problem without making any auxiliary code.

• Composites Research
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• v.24 no.3
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• pp.31-38
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• 2011

In this paper, a novel hybrid composite shield to protect space structures from hypervelocity impact of micrometeoroid and space debris is proposed. The finite element model of the proposed shield was constructed and finite element analysis was conducted to approximate the energy absorption rate. Before the final model analysis, analysis of each component including the aluminum plate, PMMA plate, and intermediate layer of fabric was performed, verifying the finite element model of each component. The material properties used in the analyses were predicted material property values for high strain rates. The analysis results showed that, other than the fabric, the energy absorption rate of each component was in agreement. Afterwards, the finite element model of the hybrid composite shield was constructed, where it was analyzed for the restrained and unrestrained fabric boundary condition cases. Through the finite element analysis, the fiber pullout mechanism was realized for the hybrid shield with free boundary inserted fabric, and it was observed that this mechanism led to energy absorption increase.

• Composites Research
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• v.32 no.5
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• pp.258-264
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• 2019

In this paper, a progressive failure analysis method was developed using the Hashin failure criterion and crack band model. Using the failure criterion, the failure initiation was evaluated. If the failure initiation is occurred, the damage variables at each failure modes (fiber tension & compression, matrix tension & compression) was calculated according to linear softening degradation behavior and the variables are used to derive the damaged stiffness matrix. The damaged stiffness matrix is reflected to damaged material and the progressive failure analysis is continued until the damage variables to be 1 that complete failure of material. A series of processes were performed using FE commercial code ABAQUS with user defined material subroutine (UMAT). To evaluate the proposed progressive failure model, the experimental results of open hole composite laminate tests was compared with numerical result. Using digital image correlation system, the strain behavior also was compared. The proposed numerical results were coincided well with the experimental results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.1
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• pp.21-29
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• 2017

In this paper, the total procedure for composite laminate mechanical joint (ASTM D5961 Proc. A, B) from fixture design to test analysis was showed. Composite laminate mechanical joints were analyzed using the FEM(Finite Element Method) and compared to test results. A progressive failure analysis was applied to FEM to analyze the failure behavior of test specimens. Three failure theories - maximum stress, maximum strain, and Tsai-Wu were applied to FEM to predict test failure load. General parameters for composite laminate joints were reviewed and the differences of bearing strength were compared with major parameters.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.10
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• pp.4673-4678
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• 2011

In this paper, studies on a mixing characteristic and viscosity measurement of polymer/graphite composites for a bipolar plate of the polymer electrolyte membrane fuel cell were presented. Since the materials for the bipolar plate should be electrically conductive, contents of solid graphite in the composite are very high. As a consequence, a viscosity of the polymer/graphite composite used for the bipolar plate is very high and the measurement of the viscosity is difficult. Viscosity measurements of the polymer/graphite composites were not possible because pressure drops were continuously fluctuated during the viscosity measurements when a conventional capillary die was used. After the die design was optimized, the steady state pressure drop could be achieved, but the viscosity thus measured was not reproducible. After many trials with different experimental techniques, it was found that melt blending of the grinded powder mixtures of both PET and graphite provides reproducible viscosity measurements and electric conductivities of the polymer/graphite composites.