• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.1
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• pp.1-10
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• 2017

In reverse engineering, one of the main tasks is reconstructing the mechanical properties of used materials. For an isotropic material, it could be defined by a single tensile test using a coupon extracted from the structure. In contrast, CFRP composites require many tests and complex procedures to define all the material properties because CFRP is an orthotropic material and a stacked laminate. In this paper, the procedure to reconstruct composite material properties is studied by using the classical lamination theory and the test data of three different laminates from a composite structure. A sample reconstruction of composite material properties using a composite car body is introduced to verify the method.

• Journal of the Korean Society for Railway
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• v.10 no.1 s.38
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• pp.39-44
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• 2007

This rafer explains a durability test of a large train car body made of carbon/epoxy composite material. The composite car body with the length of 23m was manufactured as a sandwich structure composed of an aluminum honeycomb core and CF1263 woven fabric carbon/epoxy faces. In order to evaluate durability of the composite car body, it was excited by two 500kN capacity hydraulic actuators installed underneath the body bolster. The natural frequency of the composite car body under full weight condition was found to be 4.33Hz. Based on this result, the excitation frequency and displacement of 5Hz and ${\pm}1.0mm$, respectively, were used as inputs for the durability test. The test was conducted for $2{\times}10^6$ cycles. During the test, the nondestructive tests using X-ray radiography and dye penetration method was performed to determine the presence of the cracks. Upon completion of the test, no cracks were found.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.55-60
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• 2010

The honeycomb composite joint structure designed for application to a tilting KTX railroad car body is subjected to bending loads of a cantilever type. Honeycomb sandwich composite panel-joint attached in the real tilting car body was fabricated and sectioned as several beam-joint specimens for the bending test. The fracture behaviors of these specimens under static loads were different from those under cyclic loads. Static bending loads caused shear deformation and fracture in the honeycomb core region, while fatigue cyclic bend loading caused delamination along the interface between the composite skin and the honeycomb core, and/or caused a fracture in the welded part jointed with the steel under-frame. These fracture behaviors could occur in other industrial honeycomb composite joints with similar sub-structures, and be used for improving design parameters of a honeycomb composite joint structure.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.2 s.257
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• pp.166-173
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• 2007

Fatigue fracture behavior of a hybrid bolted joint was evaluated in comparison to the case of static fracture. Two kinds of specimens were fabricated for the mechanical tests; a hybrid bolted joint specimen for the shear test and a hybrid joint part specimen applied in the real tilting car body for the bending test. Characteristic fracture behaviors of those specimens under cyclic toads were obviously different from the case under static loads. For the hybrid bolted joint specimen, static shear loading caused the fracture of the bolt body itself in a pure shear mode, whereas cyclic shear loading brought about the fracture at the site of local tensile stress concentration. For the hybrid joint part specimen, static bend loading caused the shear deformation and fracture in the honeycomb core region, while cyclic bend loading did the delamination along the interface between composite skin and honeycomb core layers as well as the fracture of welded joint part. Experimental results obtained by static and fatigue tests were reflected in modifications of design parameters of the hybrid joint structure in the real tilting car body.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.65-68
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• 2003

Using composite materials for lilting train system has many advantages such as manufacturing variety, specific high-strength & stiffness characteristics, and long-life durability, but the strongest advantage could be the possibility of lightweight product. In the leading countries, the composite materials are used for the material fer drivers' cabs, interior/exterior equipments for railway train, and it is now developing the composite materials applied for the train car body structure. In this paper, we examine the use of composite materials for the drivers' cabs and interior/exterior equipments for the developing tilting train in Korea, and review the car body design using composite materials.

• Journal of Welding and Joining
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• v.33 no.3
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• pp.12-18
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• 2015

The ultimate goal of developing body is revealed the "lightweight" at latest EuroCarBody conference 2012 and the most core technology is joining process to make lightweight car body design. Accordingly, in this study, the car body assembly line for the assembly process applies to any introduction, particularly in the assembly of aluminum alloy and composite materials applied by the process for the introductory approached. Process were largely classified by welding (laser, arc, resistance, and friction stir welding), bonding (epoxy bonding) and mechanical fastening (FDS, SPR, Bolting and clinching). Applications for each process issues in the case and the applicable award was presented, based on the absolute strength of the test specimens and joining characteristics for comparative analysis were summarized. Finally, through this paper, we would tried to establish the characteristics of the joint for lightweight structure.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.616-621
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• 2004

In this paper, the crush characteristics of a tilting train express (TTX) M-car design are evaluated with a head-on collision scenario. Its body shell is divided into three parts - front end, middle section, and rear end. For each part, crush-force relation is evaluated numerically through 3-dimensional shell element analysis with LS-DYNA. TTX's embody structure is a hybrid type structure made of steel and composite materials. Composite sandwich panels are modeled as layered shells whose layers have different material properties. And a damage material model is used to consider the effect of stiffness degradation during deformation. The crush characteristics obtained from these calculations will be used as material modeling data of full-rake collision analyses.

• Journal of Auto-vehicle Safety Association
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• v.11 no.1
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• pp.23-29
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• 2019

Recently, use of composite materials has been increasing for body structures and chassis parts in the car industry because of weight reduction effect and excellent mechanical thermal characteristics. However, application of composite materials in brake system is very difficult because it is hard to obtain enough brake performance due to low heat storage capacity of the composite materials. In this paper, we will present new carbon ceramic composite disc with high flow characteristic. To obtain this characteristic, new vent structures were designed by using ARIZ method and substance-field model analysis. The flow effect of these vent structures on the brake performance was verified by pugh matrix and cooling test. The test results show improvement of cooling performance up to $30^{\circ}C$. Finally, These results will improve brake the reliability of the brake performance for the high performance vehicles and electric vehicles.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.627-632
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• 2010

Recently the research for lightening the railway vehicle is actively made according to the demand of the environment-friendly technology development contributing to the energy cost reduction and the green growth. The railway vehicle lightweight research is expanded to the load-supporting first structure from the secondary structure which doesn't support the load. After the composite car body development used in the Korean tilting train is completed, the composite bogie frame development in which the weight reduction efficiency is large is progressed. In this paper, distributed strain was monitored when the train load was added to the central part of the composite bogie side-frame. By using the optical fiber which was attached to the lower part of the side-frame and the developed Brillouin correlation domain analysis (BOCDA) system, the strain distribution could be measured with 3cm step over 3m section. This strain distribution was compared with the design value by the FE analysis when the load of 14ton and 18ton added. This experiment can verify the manufactured composite bogie side-frame.

• Journal of the Korean Society for Railway
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• v.12 no.1
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• pp.110-114
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• 2009

This study is for the evaluation of compressive strength restoration of sandwich composite laminates with adhesively bonded scarf patches. It was used in this study that the sandwich composite laminate with an aluminum honeycomb core and CF1263 woven fabric carbon/epoxy faces was applied to the car body structure for Korean tiling train. In this study, it was damaged by low velocity impact and repaired using scarf repair method. Then, the compressive strength restoration of assessed by compressive after impact (CAI) test. From the test, it could be known that the compressive strength was restored up to 72% by only scarf repair method and 91% applied by an extra ply over the undamaged one.