• Journal of the Korean Society for Railway
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• v.13 no.4
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• pp.382-388
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• 2010

This paper describes the standardized finite element model for carbody structures of railway vehicle made of sandwich composites. Recently, sandwich composites were widely used to railway vehicle due to the improvement of energy efficiency, high specific stiffness and strength, weight reduction and space saving in korea. Therefore, structural integrity should be verified using finite element analysis prior to the manufacture of composite railway vehicle. The standardized finite element model for composite carbody structures was introduced through comparing the results of real structural test under vertical, compressive, twisting load and natural frequency test of various railway vehicles in this study. The results show that the quadratic shell element is suitable to model the reinforced metal frame used to improve the flexural stiffness of sandwich panel compared to beam element, and layered shell and solid element are recommended to model the skin and honeycomb core of sandwich panel compared to sandwich shell element. Also, the proposed standard finite element model has the merit of being applied to crashworthiness problem without modifications of finite element model.

• Steel and Composite Structures
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• v.7 no.6
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• pp.457-468
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• 2007

Analytical and experimental investigation on dynamic properties of extra lightweight concrete sandwich beams reinforced with various lay ups of carbon reinforced epoxy polymer composites (CFRP) are discussed. The lightweight concrete used in the core of the sandwich beams was made up of extra lightweight aggregate, Lica. The density of concrete was half of that of the ordinary concrete and its compressive strength was about $100Kg/cm^2$. Two extra lightweight unreinforced (control) beams and six extra lightweight sandwich beams with various lay ups of CFRP were clamped in one end and tested under an impact load. The dimension of the beams without considering any reinforcement was 20 cm ${\times}$ 10 cm ${\times}$ 1.4 m. These were selected to ensure that the effect of shear during the bending test would be minimized. Three other beams, made up of ordinary concrete reinforced with steel bars, were tested in the same conditions. For measuring the damping capacity of sandwich beams three methods, Logarithmic Decrement Analysis (LDA), Hilbert Transform Analysis (HTA) and Moving Block Analysis (MBA) were applied. The first two methods are in time domain and the last one is in frequency domain. A comparison between the damping capacity of the beams obtained from all three methods, shows that the damping capacity of the extra lightweight concrete decreases by adding the composite reinforced layers to the upper and lower sides of the beams, and becomes most similar to the damping of the ordinary beams. Also the results show that the stiffness of the extra lightweight concrete beams increases by adding the composite reinforced layer to their both sides and become similar to the ordinary beams.

• Computers and Concrete
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• v.25 no.5
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• pp.383-400
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• 2020

Due to higher stiffness to weight, higher corrosion resistance, higher strength to weight ratios and good durability, concrete composite structures provide many advantages as compared with conventional materials. Thus, they have wide applications in the field of concrete construction. This research focuses on the structural behavior of steel-tube CFRP confined concrete (STCCC) columns under axial concentric loading. A nonlinear finite element analysis (NLFEA) model of STCCC columns was simulated using ABAQUS which was then, calibrated for different material and geometric models of concrete, steel tube and CFRP material using the experimental results from the literature. The comparative study of the NLFEA predictions and the experimental results indicated that the proposed constitutive NLFEA model can accurately predict the structural performance of STCCC columns. After the calibration of NLFEA model, an extensive parametric study was performed to examine the effects of different critical parameters of composite columns such as; (i) unconfined concrete strength, (ii) number of CFRP layers, (iii) thickness of steel tube and (iv) concrete core diameter, on the axial load capacity. Furthermore, a large database of axial strength of 700 confined concrete compression members was developed from the previous researches to give an analytical model that predicts the ultimate axial strength of composite columns accurately. The comparison of the predictions of the proposed analytical model was done with the predictions of 216 NLFEA models from the parametric study. A close agreement was represented by the predictions of the proposed constitutive NLFEA model and the analytical model.

• Composites Research
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• v.17 no.3
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• pp.15-22
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• 2004

Acoustic load generated by rocket propulsion system is one of major dynamic loads during lift-off phase so that it causes the structural failure and electronic malfunction of payloads. Acoustic loads can be greatly reduced by an appropriate acoustical design of nose faring structures. This paper deals with the acoustical design of the nose fairing structure for launch vehicle. It is well known that a honeycomb sandwich structure is a poor sound insulator because of its high specific stiffness. In this paper, the sound transmission characteristics of four kinds of honeycomb structures for noise fairing were investigated by means of numerical and experimental ways. In order to estimate transmission loss, infinite plate theory by Moore and Lyon and statistical energy analysis (SEA) method were used. The predicted results showed a good agreement with measured ones. These enabled us to determine a proper core material for nose fairing, which shows good sound insulation performance per weight.

• Journal of the Korean Society for Railway
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• v.12 no.4
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• pp.518-525
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• 2009

This paper describes the evaluation of structural performance test and finite element analysis to verify the design of Bimodal Tram made of sandwich composites. The sandwich composite applied to vehicle structure was composed of a aluminum honeycomb core and WR580/NF4000 glass fabric/epoxy laminate composite facesheet. The load tests of vehicle structure were conducted for vertical load, compressive load, torsion and modal analysis according to JlS E 7105. The structural Integrity of vehicle was evaluated by the measurement of displacement, stress and natural frequency obtained from dial gauge, strain gauge and gravity sensor, respectively. And finite element analysis using ANSYS v11.0 was done to compare with structural test. The results showed that the displacement, stress and natural frequency were in an good agreement with those of structural analysis using the proposed finite element models.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.25 no.1
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• pp.37-54
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• 1999

Planarized SiO$_2$ particles were prepared by two-step reduction method of making much smaller particles, micron-sized ones, to improve spreadability, adherence, and smoothness. Various pigments known as flaky extender usually have terrace layers on their surfaces, but SiO$_2$ Particles in this study exhibit a smooth surface structure. These single SiO$_2$ particles were used for core particles to prepare the composite particles coated with ultra fine TiO$_2$ particles by a homogeneous precipitation method. The thickness and the morphology of the deposited TiO$_2$ layer could be altered by adjusting the reactant concentrations, reaction time and temperature. The characteristics of SiO$_2$/TiO$_2$composite in the field of color cosmetics is to give a UV-cut effect and to enhance the chroma of human skin color, one of optical properties.

• The Journal of Advanced Prosthodontics
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• v.5 no.2
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• pp.104-109
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• 2013

PURPOSE. Among the surface treatment methods suggested to enhance the adhesion of resin cement to fiberreinforced composite posts, conflicting results have been obtained with silanization. In this study, the effects of silanization, heat activation after silanization, on the bond strength between fiber-reinforced composite post and resin cement were determined. MATERIALS AND METHODS. Six groups (n=7) were established to evaluate two types of fiber post (FRC Postec Plus, D.T. Light Post) and three surface treatments (no treatment; air drying; drying at $38^{\circ}C$). Every specimen were bonded with dual-curing resin cement (Variolink N) and stored in distilled water for 24 hours at $37^{\circ}C$. Shear-bond strength (MPa) between the fiber post and the resin cement were measured using universal testing device. The data were analyzed with 1-way ANOVA and by multiple comparisons according to Tukey's HSD (${\alpha}$=0.05). The effect of surface treatment, fiber post type, and the interactions between these two factors were analyzed using 2-way ANOVA and independent sample T-tests. RESULTS. Silanization of the FRC Postec Plus significantly increased bond strength compared with the respective non-treated control, whereas no effect was determined for the D.T. Light Post. Heat drying the silane coupling agent on to the fiberreinforced post did not significantly improve bond strength compared to air-syringe drying. CONCLUSION. The bond strength between the fiber-reinforced post and the resin cement was significantly increased with silanization in regards to the FRC Postec Plus post. Bond strength was not significantly improved by heat activation of the silane coupling agent.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.3
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• pp.83-90
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• 2010

Composite materials can be used economically and efficiently in civil engineering applications when standards and procedure for analysis, design, construction and quality control are to be established. Bridge systems, including the girders and cross-beams, and concrete decks behave as the specially orthotropic plates. For such systems with sections, boundary conditions other than Navier solution types, it is very difficult to obtain its analytical solution. To design the bridge made by the composite materials, cross-section was used as the form-core shape for economical reason and finite difference method was used for output of the stress value. The Tsai-Wu failure criterion for stress space is used. In this paper, the rate of tensile strength reduction due to increased size was considered. And also numerical study is made for these cases.

• Membrane Journal
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• v.31 no.2
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• pp.120-132
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• 2021

Microbial fuel cell (MFC) is a bio-electrochemical device that generates electricity by utilizing bacterial catalytic activity that degrades wastewater. Proton exchange membrane (PEM) is the core component of MFC that decides its performance, and Nafion membrane is the most widely used PEM. In spite of the excellent performance of Nafion, it has drawbacks such as high cost, biofouling issue, and non-biodegradable property. Recent studies in MFC attempted to synthetize the alternative membrane for Nafion by incorporating various polymers, sulfonating, fluorinating, and doping other chemicals. This review summarizes characteristics and performances of different composite membrane based MFCs, mostly focusing on PEM.

• Journal of Convergence for Information Technology
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• v.9 no.7
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• pp.33-40
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• 2019

As aerospace industry has been activated recently, it is required to commercialize composite analysis software. Until now, commercial software has been mainly used for analyzing composites, but it has been difficult to use due to high price and limited functions. In order to solve this problem, automatic analysis software for both in-plane and corner radius strength, which are all made on-line and generalized, has recently been developed. However, these have the disadvantage that they can not be analyzed simultaneously with multiple failure criteria. In this paper, we propose a method to greatly improve the processing speed while simultaneously handling the analysis of multiple failure criteria using a parallel processing platform that only works with a GPU equipped with a CUDA core. We have obtained satisfactory results when the analysis speed is experimented on the vast structure data.