• Composites Research
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• v.20 no.3
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• pp.25-30
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• 2007

This paper describes the basic design and fabrication of smart skin antenna for phased array applications. The smart skin phased array antenna, of which radiation pattern can be electrically steerable without mechanical rotation, has to meet the both mechanical and electrical performance. The smart skin antenna is a honeycomb sandwich structure to enhance the mechanical performance such as strength, weight and so on. The example of smart skin antenna integrated with radome is designed with the resonant frequency of 5 GHz, circular polarization, 2 by 2 subarray, and a coaxial probe-fed excitation. In addition, the performance of raw microstrip patch antenna uncovered radome is investigate. The fabricated smart skin antenna shows a reasonable performance with gain of 12.2 dBi and frequency bandwidth of 6.4 %.

• Composites Research
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• v.29 no.4
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• pp.209-215
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• 2016

The failure of composite sandwich structures with thickness and material variation was studied. The main body of the structure is sandwich plate made of the carbon composite face and Aluminum honeycomb core. It is connected with composite laminated flange without core through transition region of tapered sandwich panel with foam core. Tension and compression tests were conducted for the total of 6 panels, 3 for each. Test results showed that the panels under compression are vulnerable to the face failure along the material discontinuity line between two different cores. However the failure load of which panel does not show such failure can carry 16% more load and fails in honeycomb core and face debonding. For the tensile load, the extensive delamination failure was observed at the corner radius which connects the panel and the flange. The average failure load for compression is about 7 times the tensile failure load. Accordingly, these sandwich structures should be applied to the components that endure the compressive loadings.

• Composites Research
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• v.15 no.3
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• pp.45-51
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• 2002

Smart skin, a multi-layer structure of composed or different materials, was designed and fabricated. Tests and analyses are conducted to study the characteristics of its behavior under compression and bending loads. The designed smart skin failed due to premature buckling before compression failure. It was confirmed that shear moduli of honeycomb core affect structural stability of smart skin. A new test method and device were designed fur better measurement of shear moduli of honeycomb core. Numerical prediction of structural behavior of smart skin by NASTRAN agreed well with experimental data.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.393-394
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• 2006

This study introduces the testing results of the composite carbody which is applied to tilting train. The composite carbody is made of aluminum honeycomb structure materials like a sandwich. The static load test was performed to evaluate the structural characteristic and stability of the composite carbody. Considering the vertical, compressive, twisting load and 3-point supporting type as a testing terms, the structural stability of a carbody was evaluated.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.2073-2079
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• 2008

This study aims to investigate the residual strength of sandwich composites with Al honeycomb core and carbon fiber face sheets after the quasi-static indentation damage by the experimental investigation. The 3-point bending test and the edge-wise compressive strength test were used to find the mechanical properties. The quasi-static point load and damaged hole was applied to introduce the simulated damage on the Each damaged specimens were finally assessed by the 3-point bending test and the compressive strength test. The investigation results revealed the residual strength of the damaged specimens due to the quasi-static indentation.

• Composites Research
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• v.24 no.5
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• pp.9-16
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• 2011

This paper describes the crashworthiness evaluation and performance improvement of tilting train made of sandwich composites. The applied sandwich composite of carbody structure was composed of aluminum honeycomb core and glass/epoxy & carbon/epoxy laminate composite facesheet. Crashworthiness analysis of tilting train was carried out using explicit finite element analysis code LS-DYNA 3D. The 3D finite element model and 1D equivalent model were applied to save the finite element modeling and calculation time for crash analysis. The crash conditions of tilting train were conducted according to four crash scenarios of the Korean railway safety law. It found that the crashworthiness analysis results were satisfied with the performance requirements except the crash scenario-2. In order to meet the crashworthiness requirements for crash scenario-2, the stiffness reinforcement for the laminate composite cover and metal frames of cabmask structure was proposed. Consequentially, it has satisfied the requirement for crash scenario-2.

• 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.

• Composites Research
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• v.30 no.6
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• pp.384-392
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• 2017

Sandwich panels with three different joint configurations were tested to design a novel sandwich joint structure that can effectively support both the tensile and compressive loads. The sandwich core was mainly aluminum flex honeycomb but the PMI foam core was limitedly applied to the ramp area which is transition part from sandwich to solid laminate. The face of sandwich panel was made of carbon fiber composite. For configuration 1, the composite flange and the sandwich panel were cocured. For configurations 2 and 3, an aluminum flange was fastened to the solid laminate by HI-LOK pins and adhesive. The average compressive failure loads of configurations 1, 2, and 3 were 295, 226, and 291 kN, respectively, and the average tensile failure loads were 47.3 (delamination), 83.7 (bolt failure), and 291 (fixture damage) kN, respectively. Considering the compressive failure loads only, both the configurations 1 and 3 showed good performance. However, the configuration 1 showed delamination in the corner of the composite flange under tension at early stage of loading. Therefore, it was confirmed that the structure that can effectively support tension and compressive loads at the same time is the configuration 3 which used a mechanically fastened aluminum flange so that there is no risk of delamination at the corner.

• 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 Korean Society for Aeronautical & Space Sciences
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• v.38 no.1
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• pp.29-34
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• 2010

In this study, joint strength and failure characteristics were experimentally examined with pull-out and shear specimens in which new designed "high strength insert" was applied. The performance of the new insert was compared with typical insert design. The experimental results showed that the "high strength insert" had the joint strengths of 2.1 times in the pull-out specimens and 2.04 times in the shear specimen compared with typical insert joints. Therefore, the new developed "high strength insert" will be usefully used in the aerospace structure.