• Journal of Korean Society of Steel Construction
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• v.13 no.6
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• pp.631-640
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• 2001

The behavior of composite materials bridge 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 5 test specimens with 1/10 scale of full size were carried out. Three specimens were fabricated from sandwich upper flange and two specimens were fabricated from laminated upper flange. The constituents of bridge decks were glass fiber performs and epoxy resin. The experimental results, i.e., the maximum strength stiffness, stiffness, and deformation capacity, were summarized. The results of the finite element analysis were compared with the experimental results for the verification of validity.

• 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.

• Composites Research
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• v.32 no.5
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• pp.279-283
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• 2019

A flight training simulator of a fully spherical configuration is being developed to precisely and quickly control six degrees of freedom (Dof) motions especially with unlimited rotations. The full-scale simulator should be designed with a lightweight material to reduce inertial effects for fast and stable feedback controls while no structural failure is ensured during operations. In this study, a sandwich composite consisting of glass fiber reinforced plastics and a foam core is used to obtain high specific strengths and specific stiffnesses. T-type stainless steel frames are inserted to minimize the deformation of the sphere curvature. Finite element analysis is carried out to evaluate structural safety of the simulator composed of the sandwich sphere and steel frames. The analysis considers the weights of the equipment and trainee and it is assumed to be 200 kg. Gravity acceleration is also considered. The stresses and displacement acting on the simulator are calculated and the safety is assessed under two different situations.

• Composites Research
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• v.24 no.3
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• pp.25-30
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• 2011

The studies on the non-destructive testing methods of the composite materials are very important for improving their reliability and safety. AE(Acoustic Emission) can evaluate the defects by detecting the emitting strain energy when elastic waves are generated by the generation and growth of a crack, plastic deformation, fiber breakage, matrix cleavage or delamination. In this paper, the AE signals of the filament wound composite cylinder and sandwich cylinder during the pressure test were measured and analyzed. The signal characteristics of PVDF sensors were measured, and an AE signal analyzer which had the band-pass filter and L-C resonance filter were designed and fabricated. Also, the crack detection capability of the fabricated AE signal analyzer wes evaluated during the pressure tests of the filament wound composite cylinder and the sandwich cylinder.

• Composites Research
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• v.17 no.6
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• pp.22-27
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• 2004

The objective of this work is to design Surface Antenna Structure (SAS) and investigate fatigue behavior of SAS that is asymmetric sandwich structure. This term, SAS, indicates that structural surface becomes antenna. Constituent materials are selected considering electrical properties, dielectric constant and tangent loss as well as mechanical properties. For the antenna performance, SSSFIP elements inserted into structural layers were designed fur satellite communication at a resonant frequency of 12.5 GHz and final demonstration article was $16{\;}{\tiems}{\;}8$ array antenna. From electrical measurements, it was shown that antenna performances were in good agreement with design requirements. In cyclic 4-point bending, flexure behavior was investigated by static and fatigue test. Fatigue life curve of SAS was obtained. The fatigue load was determined experimentally at a 0.75 (1.875kN) load level, Experimental results were compared with single load level fatigue life prediction equations (SFLPE) and in good agreement with SFLPE. SAS concept is the first serious attempt at integration fur both antenna and composite engineers and promises innovative future communication technology.

• Fire Science and Engineering
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• v.29 no.6
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• pp.84-90
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• 2015

Multi-layered material (sandwich panel) consists of double-sided steel plate which is incombustible material or similar material and core material which is not incombustible material. In case of sandwich panel which uses combustible material as insulation, flames spread inside the steel plate at the time of fire so that it is difficult to extinguish fire from the outside and flames spread rapidly and may cause the building to collapse. The current Building Act requires the sandwich panel to secure fire-retardant performance according to the purpose and size of building. In this study, the fire spreading prevention structure applied to partial exterior walls was applied to multi-layered material and its effect was measured through full scale fire test and the possibility to secure fire safety of buildings by applying the fire spreading prevention structure to multi-layered material in future was presented.

• Composites Research
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• v.20 no.5
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• pp.26-33
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• 2007

Pull-out and shear strengths of insert Joints of sandwich structure were investigated by experiment. Specimens were prepared by cocuring of nomex honeycomb core and carbon-epoxy composite face using an adhesive FM73. A total of 75 specimens with 10 different types depending on the core height and density, face thickness, and loading direction were tested. In the test under pull-out loading, although both the core height and density affect the failure loads, the effect of cell density is more serious. Dominant factor fur failure loads of the joints under shear loading is face thickness and the effect of core height is negligible. In the joint with same dimension, failure loads vary depending on the potted area of the core, particularly in the pull-out test.

• Composites Research
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• v.14 no.3
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• pp.69-76
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• 2001

This paper proposes a double cantilever sandwich-beam method fur evaluating the frequency dependence of dynamic characteristics of rubbers. The flexural vibration of a double cantilever sandwich-beam specimen with an inserted rubber layer was studied using a finite element simulation in combination with the sine-sweep test. Quadratic relationships of dynamic elastic modulus and material loss factor of rubbers with frequency were suggested employing the least square error method.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.3
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• pp.56-65
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• 1996

Recently, with development of mechanics of materials, as pursuing the high speed of the ships, there has been an increasing demand on the composite construction which satisfies high strength and low weight at the same time. A sandwich element is a type of composite construction, which is composed of thin, strong, stiff and relatively high density faces and a thick, light, and weaker core material. As the second moment is increased by faces separated from the neutral axis farther, a sandwich element is most effective light structural form. In this study, Rayleigh-Ritz Energy Method is adopted, which can analyze sandwich plate relatively simply and exactly. Stresses and buckling loads are analyzed exactly, when uniform lateral pressure load, inplane compression and inplane shear are acting at the sandwich plate. Including a wrinkling stress, this study can be applied to the initial design and minimum weight design of sandwich plates.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.224-227
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• 2001

Adaptive analysis of multilayered composite and sandwich plates is carried out. The adaptive analysis is based on a finite element error form, which measures the difference between the through-the-thickness distribution of finite element displacement and the actual displacement. The region where the error-measure exceeds the prescribed admitted error value, the finite element mesh locally refined in the thickness direction using the mesh superposition technique. Several numerical tests are conducted to validate the effectiveness of the current approach for adaptive analysis of laminated plates.