• 연구논문집
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• s.30
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• pp.129-135
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• 2000

Double boss type composite pressure bottles have been developed widely but single boss type had not because there are some difficulty in technical point. In this paper a research was performed to develop composite pressure vessel in conjunction with design, fabrication, and test. Fiber pattern and angles were decided by CADFIL software and they are [liner/$15^{\circ}$/$15^{\circ}$/$90^{\circ}$/$18^{\circ}$/$90^{\circ}$/$21^{\circ}$/$21^{\circ}$/$90^{\circ}$]. Fabrication of bottles was done by AEA's 5-axis filament winding machine. During fabrication fiber optic sensor were embedded to measure were behavior of structure at the applied internal pressure. Even though satisfied test results were not obtained, the experimental set-up of fiber optics showed the possibility for the application of filament wound vessels. However, the conventional strain and fabrication of single boss composite bottles.

• Steel and Composite Structures
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• v.35 no.2
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• pp.171-186
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• 2020

This paper aims at providing insights on the use of thermosetting liner for the repair of offshore pipelines exposed to corrosion and leakage. The work which covers both experimental and numerical approaches were aspired due to the high cost of repair for pipelines, limitations of thermoplastic material and limited study of reinforced thermosetting liner. The experiment involves a destruction test called the burst test, carried out on an API 5L X42 carbon steel pipe under four case studies, namely (i) intact pipe, (ii) pipe with corrosion defect, (iii) pipe with corrosion defect and repaired with thermosetting liner and (iv) pipe with leakage and repaired with thermosetting liner. The numerical simulation was developed to first validate the experimental results and later to optimize the design of the thermosetting liner in terms of the number of layers required to restore the original strength of the pipe. The burst test shows an improvement in 23% of the burst capacity for the pipe with corrosion defects, after being repaired with a three-layer thermosetting liner. The parametric studies conducted showed that with an addition of thermosetting layers, the burst capacity improves by an average of 1.85 MPa. In conclusions, the improvement in strength can be further increased with increasing thickness of the thermosetting liner. The thermosetting liner was also determined to fail first inside the host pipe.

• Journal of the Korean Institute of Gas
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• v.15 no.1
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• pp.35-39
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• 2011

The purpose of this paper is to analyze affecting ratios of strength safety in carbon fiber layer thickness of a composite fuel tank for FEV vehicles. To investigate affecting ratios by FEM modeling, the equivalent von Mises stress has been computed on the aluminum liner and carbon fiber layers of composite fuel tanks in hoop and helical directions respectively. According to the FEM results, the affecting ratios of an aluminum liner on the equivalent stress are 77.5% in hoop direction, 18.11% in $70^{\circ}C$ winded helical direction and 4.39% in $12^{\circ}C$ winded helical direction. These trends on the strength safety of carbon fiber layers have been shown as those of an aluminum liner even though the layer thickness ratio of $12^{\circ}C$ inclined carbon fiber is very high of 42% compared with that of hoop layer thickness. Thus, the computed results show that the strength safety of a carbon fiber fuel tank is more influenced by the winding angle rather than the fiber thickness of carbon fiber layers.

• Journal of the Korean Institute of Gas
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• v.15 no.5
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• pp.37-41
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• 2011

This paper presents the strength safety of a hydrogen gas composite fuel tank, which is analyzed using a FEM based on the criterion of US DOT-CFFC and Korean Standard. A hydrogen gas composite tank in which is fabricated by an aluminum liner of 6061-T6 material and carbon fiber wound composite layers of T800-24K is charged with a filling pressure of 70MPa and a gas storage capacity of 130 liter. The FEM results indicated that von Mises stress, 255.2MPa of an aluminum liner inner tank is low compared with that of 95% yield strength, 272MPa. And a carbon fiber stress ratio of a composite fuel tank is 3.11 in hoop direction and 3.04 in helical direction. These data indicate that a carbon fiber gas tank is safe in comparison to that of a recommended criterion of 2.4 stress ratio. Thus, the proposed composite tank with 130 liter capacity and 70MPa filling pressure is usable in strength safety.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.165-168
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• 2007

The objective of this study is to demonstrate and commercialized for on-board fuel storage system for the hydrogen fuel cell vehicles. Type3 composite cylinder is consisting of the full wrapped composites on a seamless aluminum liner. Especially, the seamless aluminum liner has been commercialized with development of fabrication through this study. The key technologies, including design, analysis and the optimized filament winding process for 350bar composite cylinder, were established and verified with design qualification test in accordance with international standard. And the facilities for fabrication and design qualification test have been constructed.

• Structural Engineering and Mechanics
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• v.27 no.3
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• pp.277-292
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• 2007

Based on the composite finite element simulation and a series of hydrostatic pressure and burst tests, autofrettage effects on strength and deformation of fiber reinforced pressure vessel with metallic liners have been studied in the paper (autofrettage: during the course of one pressure taking effect, the increasing internal stress in metallic liner can surpass the yielding point and the plastic deformation will happen, which result in that when there is no internal pressure, there are press stress in liner while tensile stress in fiber lamination). By making use of a composite finite element Ansys code and a series of experiments, the autofrettage pressure is determined in order to make the aluminium liner be totally in elastic state, under given hydrostatic test pressure. The stress intensity factors of the longitudinal crack in aluminum liner end under internal pressure and thermal loads have been computed and analyzed before and after the autofrettage processing. Through numerical calculation and experiment investigations, it is found that a correct choice for autofrettage pressure can improve the gas-tightness and fatigue strength of FRP vessel.

• Steel and Composite Structures
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• v.44 no.3
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• pp.423-436
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• 2022

This paper proposes an innovative thin-walled square concrete filled steel tubular (CFST) column with an octagonal/circular lining steel tube, in which the outer steel tube and the inner liner are fabricated independently of each other and connected by slot-weld or self-tapping screw connections. Twelve thin-walled square CFST columns were tested under quasi-static loading, considering the parameters of liner type, connection type between the square tube and liner, yield strength of steel tube, and the axial load ratio. The seismic performance of the thin-walled square CFST columns is effectively improved by the octagonal and circular liners, and all the liner-stiffened specimens showed an excellent ductile behavior with the ultimate draft ratios being much larger than 1/50 and the ductility coefficients being generally higher than 4.0. The energy dissipation abilities of the specimens with circular liners and self-tapping screw connections were superior to those with octagonal liner and slot-weld connections. Based on the test results, both the finite element (FE) and simplified theoretical models were established, considering the post-buckling strength of the thin-walled square steel tube and the confinement effect of the liners, and the proposed models well predicted the hysteretic behavior of the liner-stiffened specimens.

• Journal of the Korean Institute of Gas
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• v.16 no.3
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• pp.16-21
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• 2012

In this study, the strength safety for 110 liter hydrogen fuel storage tank with 70MPa filling pressure has been analyzed using a FEM technique. The strength safety of a composite fuel tank in which is fabricated by an aluminum liner of 6061-T6 and carbon fiber wound composite layers of T800-24K and T700-12K of Toray, and MR60H-24P of Mitsubishi Ray has been investigated based on the criterion of a strength safety of US DOT-CFFC and Korean Standard. The FEM computed results on the strength safety of 70MPa hydrogen gas tank showed that the hydrogen fuel storage tank in which is fabricated by T800-24K and T700-12K of Toray, and MR60H-24P of Mitsubishi Ray is safe because those two carbon fibers have very similar material properties. But, the composite storage tank with a filling pressure of 70MPa in which is fabricated by T700-12K of Toray may not guaranty the strength safety, and thus this study recommends a composite hydrogen fuel tank under 60MPa.

• Composites Research
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• v.35 no.3
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• pp.147-152
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• 2022

Low-temperature characteristics according to internal temperature conditions during rotational molding of Type 4 pressure vessel liners were studied in this paper. Since rotational molding has a sensitive effect on the formability of the liner depending on the temperature conditions, the temperature conditions for the polyamide used should be accurately set. The structural changes of polyamide as the liner material was analyzed the surface by atomic force microscope (AFM), and the crystallinity measured with a differential scanning calorimeter (DSC) is used to evaluate the change of the mechanical strength value at low temperature. In addition, the formability of the liner was confirmed by observation of the yellow index inside the liner. As a result, as the melting range of the internal temperature becomes wider, the yellow index shows a lower value, and the elongation and impact characteristics at low temperatures are improved. It was also confirmed that the structure of the polyamide was uniform and the crystallinity was high by AFM and DSC. These experimental results contribute to the improvement of characteristics at low temperatures due to changes in temperature conditions during rotational molding.

• Journal of the Korean Institute of Gas
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• v.15 no.6
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• pp.57-62
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• 2011

In this study, the optimized design for 130 liter storage fuel tank with 70MPa filling pressure has been investigated using a FEM technique and Taguchi design method. The strength safety of a composite fuel tank in which is fabricated by an aluminum liner of 6061-T6 material and carbon fiber wound composite layers of T800-24K has been analyzed based on the criterion of design safety of US DOT-CFFC and Korean Standard. The FEM computed results on the stress safety of 70MPa hydrogen gas tank were compared with a criterion of a stress ratio, 2.4 of US DOT-CFFC and Korean Standard, and indicated the safety. Thus, the optimized design elements based on the Taguchi's method were recommended as an aluminum liner thickness of 6.4mm, a carbon fiber laminate thickness in hoop direction of 31mm and a carbon fiber laminate thickness in helical direction of 10.2mm, which is represented by a design model of No. 5.