• Smart Structures and Systems
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• v.19 no.6
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• pp.633-641
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• 2017

The complexity of macro-fiber composite (MFC) materials increasing the difficulty in simulation and analysis of MFC integrated structures. To give an accurate prediction of MFC bonded smart structures for the simulation of shape and vibration control, the paper develops a linear electro-mechanically coupled static and dynamic finite element (FE) models based on the first-order shear deformation (FOSD) hypothesis. Two different types of MFCs are modeled and analyzed, namely MFC-d31 and MFC-d33, in which the former one is dominated by the $d_{31}$ effect, while the latter one by the $d_{33}$ effect. The present model is first applied to an MFC-d33 bonded composite plate, and then is used to analyze both active shape and vibration control for MFC-d31/-d33 bonded plate with various piezoelectric fiber orientations.

• Journal of Korean Society of Steel Construction
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• v.29 no.1
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• pp.61-71
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• 2017

The flexural behavior of composite ring stiffened by GFRP and steel pipe is presented in this paper. The effective width is required to construct FEM beam element model to verify the composite flexural behavior of stiffened ring of cylindrical shell structure. The experimental results are compared with the theoretical and FEM results by commercial program ABAQUS to verify the effective width coefficient. The yield, crack and ultimate loads is calculated using theoretical strains that varies depending on yield state and compared with experiment result and FEM results by ABAQUS solid model.

• Transactions of Materials Processing
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• v.23 no.8
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• pp.482-488
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• 2014

Flexible forming technology has advantages in sheet metal forming, because it can be implemented to produce various shaped molds using a single apparatus. Due to this advantage, it is possible to apply it to the manufacture of an aircraft winglet mold. Presently, most aircraft winglets are manufactured from composite materials. Therefore, the mold for the curing process is an essential element in the fabrication of such composite materials. Compared to conventional mold forming, flexible forming has some advantages such as reduced manufacturing cost and uniformity of mold thickness. If the thickness of the mold is consistent, then the heat transfer will occur uniformly during the curing process leading to improved formability of the composite material. In the current study, numerical simulations were performed to investigate the possibility of flexible forming for manufacturing of the winglet mold. In order to match the size of the actual product, the shape of objective surface was divided to fit the dimensions of the apparatus. The results from the numerical simulations are compared with the objective surface to verify the accuracy. In conclusion, the current study confirms the feasibility and the potential to manufacture winglet molds by flexible forming.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.351-359
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• 2010

Large PHC piles with a diameter of 1,000mm or larger were recently introduced for the first time in Korea. This paper presents full-scale static and dynamic pile load tests performed on two 1,000mm PHC piles and two composite piles with steel pipe piles of the same diameter in the upper portion, installed by driving and pre-boring. The objectives of the tests include evaluating pile drivability, load-settlement relation, allowable bearing capacity, and the stability of mechanical splicing element for the composite pile(a.k.a. non-welding joint). The performance of the large diameter PHC piles were thought to be satisfactory compared to that of middle sized PHC piles with a long history of successful applications in the domestic and foreign markets.

• Composites Research
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• v.14 no.3
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• pp.10-17
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• 2001

A reseach was peformed to develop composite pressure vessels in conjunction with design, fabrication, and test. Fiber pattern and angels were decided by CADFIL software and they were [$liner/15^{\circ}/15^{\circ}/90^{\circ}/18^{\circ}/90^{\circ}/21^{\circ}/21^{\circ}/90^{\circ}$]. Fabrication of bottles were done by 5-axis filament winding machine. During fabrication fiber optic sensors were embedded to measure the strain at points when internal pressure was applied by water pump. Conventional strain gage instrumentation showed the stable test results. The test results were compared to finite element analysis results and they were close each other in strain values. One can see the successful design and fabrication of single boss composite vessels.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.127-131
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• 2003

KARI developed 50m class unmanned airship. The airship employ the pressure envelope design principle. The envelope must be considered as a main structural element of the airship. The envelope ＆ three ballonets are fabricated by polyfiber composite laminates. Other structural components (gondola, tailwing, nosecone ＆ engine mounts) are manufactured by carbon fiber ＆ glass fiber laminates. In order to develop a big unmanned airship, a large amount of structural design, analysis and tests had to be made. The paper describes the structural configuration of the 50m class uumanned airship which are basic starting point of the structural development of an airship. The paper includes the various designing processes, components development tests and analysis results. Envelope ＆ ballonets development processes which are very different to conventional airplane design are given in details with actual analysis & test results. The paper also describes the structural design and analysis results for other composite made structures. Each components were tested by static design limit loads and structural safety were confirmed. The paper shows the manufactured structural components and assembled airship.

• Composites Research
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• v.25 no.6
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• pp.217-223
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• 2012

This study investigates a geometrical nonlinear dynamic behaviors of laminated skew plates made of advanced composite materials (ACM). Based on the first-order shear deformation plate theory (FSDT), the Newmark method and Newton-Raphson iteration are used for the nonlinear dynamic solution. The effects of cutout sizes, skew angles and lay up sequences on the nonlinear dynamic response for various parameters are studied using a nonlinear dynamic finite element program developed for this study. The several numerical results were in good agreement with those reported by other investigators for square composite plates with or without central cutouts, and the new results reported in this paper show the significant interactions between the cutout, skew angles and layup sequence in the laminate. Key observation points are discussed and a brief design guideline of skew laminates is given.

• Composites Research
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• v.25 no.6
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• pp.186-190
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• 2012

With the wide application of fiber-reinforced composite material in aero-structures and mechanical parts, composite joint have become a very important research area because they are often the weakest sites in composite structures. In this paper, the failure strengths of the bolted joint and pin joint which have variable hole clearance were evaluated and compared. From the tests, the first failure loads of the bolted joint and pin joint with $880{\mu}m$ hole clearance have decreased by 24.2 % and 51.3 % compared to those of joints with $0{\mu}m$ hole clearance, respectively. Also, the failure index of the joints were calculated by the finite element method and compared with experimental results.

• Composites Research
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• v.25 no.6
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• pp.191-197
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• 2012

In this paper, the penetration behavior of carbon/epoxy composite laminates subjected to high velocity projectile impact was studied by numerical simulation. The composite laminates made of carbon/epoxy with $[45/0/-45/90]_{ns}$ stacking sequence and the spherical steel impactor were three-dimensionally modeled. The ply numbers of 16 and 24 and the impact velocities in the range of 140-250 m/s were considered. The analysis was performed using an explicit finite element code LS-DYNA. The residual velocity and the amount of damage were predicted and compared to the experimental results.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.212-213
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• 2005

The results of an experimental and analytical study of composite pressure hull on buckling pressure are presented for URN 300. We predicted the buckling and post buckling analysis of composite laminated cylindrical shell and panel under external compression by using ABAQUS/Standard[Ver 6.4]. To obtain nonlinear static equilibrium solutions for unstable problems, where the load-displacement response can exhibit the type of nonlinear buckling behavior, during periods of the response, the load and/or the displacement may decrease as the solution evolves, used the modified Riks method. Experiments were conducted to verify the validation of present analysis for cross-ply laminated shells. The shells considered in the study have four different lamination patterns, [${\pm}{\Theta}$/0/90]$_{14s}$,[${\pm}{\Theta}_{14}$/$0_{14}$/$90_{14}$],[${\pm}$45/0/90]$_{18s}$ and [/0/90]$_{18s}$. At the result of this study, the optimized ply orientation angle is $75^{\circ}$. The critical load from experiment is 69% of that of numerical analysis, because the fracture of matrix was generated before buckling. So URN 300 is not proper to use at the condition under high external pressure.