• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.381-382
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• 2006

The mechanical behaviors of multi-layered foam core sandwich composite were investigated through a 3-point bending test. The sandwich specimens were obtained from sandwich panel consisting of aluminum faces and urethane foam core. Three types of sandwich specimens such as a single structure, a double structure and a triple structure were considered. The span of sandwich specimens were varied from 170mm to 350mm. According to the results, the flexural and shear properties of multi-layered sandwich composite were found to be higher than those of single-layered sandwich composite.

• 한국재료학회지
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• 제31권6호
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• pp.331-338
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• 2021

Ti-Al-Si target and Cr-Si target are sputtered alternately to develop a multi-layered nitride coating on a steel mold to improve die-casting lifetime. Prior to the multi-layer deposition, a CrN layer is developed as a buffer layer on the mold to suppress the diffusion of reactive elements and enhance the cohesive strength of the multi-layer deposition. Approximately 50 nm CrSiN and TiAlSiN layers are deposited layer by layer, and form about three ㎛-thickness of multi-layered coating. From the observation of the uncoated and coated steel molds after the acceleration experiment of liquid metal injection casting, the uncoated mold is severely eroded by the adhesion of molten metallic glass. On the other hand, the multi-layer coating on the mold prevents element diffusion from the metallic glass and mold erosion during the experiment. The multi-layer structure of the coating transforms the nano-composite structured coating during the acceleration test. Since the nano-composite structure disrupts element diffusion to molten metallic glass, despite microstructure changes, the coating is not eroded by the 1,050 ℃ molten metallic glass.

• Steel and Composite Structures
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• 제53권1호
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• pp.77-90
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• 2024

This paper focuses on trigonometric porosity distribution to analyze its effect on the free vibration frequencies of porous orthotropic multi-layered composite plates. Three types of porosity distributions are considered. The governing equations of the free vibration response of porous orthotropic multi-layered composite plates are derived from the Hamilton's principle using higher-order shear deformation theory. The free vibration frequency relation of the problem is obtained by performing Galerkin's method. After the validation process of the relation under the available literature, a few parametric analyses are performed to observe the influence of shear deformation, porosity distribution, orthotropy, layer sequence, and different geometric properties on the frequencies.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.176-179
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• 2001

When the preform is composed of more than two layers with different in-plane permeability in resin transfer molding, effective average permeability should be determined for the flow analysis in the mold. The most frequently used averaging scheme is the weighted average scheme, but it does not account for the transverse flow between adjacent layers. A new averaging scheme is proposed predicting the effective permeability of the multi-layered preform, which accounts for the transverse flow effect. The new scheme is verified by measuring the effective permeability of the multi-layered preforms and the difference in each flow front position.

• 항공우주시스템공학회지
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• 제15권6호
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• pp.59-65
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• 2021

In this paper, the transmission characteristics of the multi-layered composite material with wire mesh and honeycomb core for aircraft applications have been analyzed with the proposed method. The proposed method converts the conductive wire mesh into effective layer, while for the dielectric honeycomb core, effective permittivity has been derived based on volume fraction with the proposed method. The proposed method has been verified through comparison with full-wave simulation and revealed excellent. In addition, the calculation time of the proposed method is a few order of magnitude faster in comparison with the full-wave simulation.

• Korea-Australia Rheology Journal
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• 제18권4호
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• pp.217-224
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• 2006

Rapid flow advancement without void formation is essential in the liquid composite molding (LCM) such as resin transfer molding (RTM) and vacuum assisted resin transfer molding (VARTM). A highly permeable layer in multi-layered preform has an important role in improvement of the flow advancement. In this study, a multi-layered preform which consists of three layers is employed. Radial flow experiment is carried out for the multi-layered preform. A new analytic model for advancement of flow front is proposed and effective permeability is defined. The effective permeability for the multi-layered preform is obtained analytically and compared with experimental results. Compaction test is performed to determine the exact fiber volume traction of each layer in the multi-layered preform. Transverse permeability employed in modeling is measured experimentally unlike the previous studies. Accurate prediction of flow advancement is of great use for saving the processing time and enhancing product properties of the final part.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.137-140
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• 2005

Resin transfer molding (RTM) is one of the most popular processes for producing fiber reinforced polymer composites. In the manufacture of complex thick composite structures, analysis on flow front advancement on the resin impregnating the multi-layered fiber preform is helpful for the optimization of the process. In this study, three-dimensional mold filling simulation of RTM is carried out by using CVFEM (Control Volume Finite Element Method). On the assumption of isothermal flow of Newtonian fluid, Darcy’s law and continuity equation are used as governing equations. Different permeability tensors employed in each layer are obtained by experiments. Numerically predicted flow front is compared with experimental one in order to validate the numerical results. Flow simulations are conducted in the two mold geometries, rectangular plate and hollow cylinder. Permeability tensor of each layer preform in Cartesian coordinate system is transformed to cylinder coordinates system so that the flow within the multi-layered preforms of the hollow cylinder can be calculated exactly. Our emphasis is on the three dimensional flow analysis for circular three-dimensional braided preform, which shows outstanding mechanical properties such as high impact strength and toughness compared with other conventional two-dimensional laminar-structured preforms.

• Composites Research
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• 제22권3호
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• pp.66-73
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• 2009

적층 두께, 면밀도, 질량관성모우멘트는 소재의 구조-역학적 특성을 나타내는 중요한 인자들이다. 본 연구에서는 이와 같은 인자들이 다층-복합재료구조의 내충격 성능에 미치는 영향을 고찰하기 위해 높은 충격자 속도 하에서 탄자한계속도기 최대가 되는 재료-구조 최적화를 수행하였다. 세라믹복합재료, 고무, 알루미늄 그리고 알루미늄 폼으로 구성된 다층-복합재료구조의 최적화를 위해 Florence 모델과 Awerbuch-Bonder 모델을 연계한 통합 모델을 개발하였으며, 구속 조건으로써 적층 두께, 면밀도, 질량관성모우멘트를 함께 사용하였다. 결과에서 알 수 있듯이, 제안된 통합 모델을 통해 계산된 탄자한계속도는 유한표소해석에서의 탄자한계속도와 거의 유사함을 확인하였다. 통합 모델을 바탕으로 재료-구조 최적화를 통해 설정된 다층구조는 최적화를 수행하지 않은 다층구조에 비해 약 10.8%의 탄자한계속도 및 26.7%의 충격흡수에너지 향상이 나타남을 알 수 있다.

• 복합신소재구조학회 논문집
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• 제3권4호
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• pp.17-26
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• 2012

This study presents a governing equations of bending behavior of anisotropic sandwich plates with multi-layered laminated composite faces. Based on zig-zag models for through thickness deformations, the shear deformation of composite faces is included. All edges of plate are assumed to be simply supported. Results of the bending analysis under lateral loads are presented for the influence of various lay up sequences of antisymmetric angle-ply laminated faces. The accuracy of the approach is ascertained by comparing solutions from the sandwich plates theory with composite faces to the laminated plates theory. Since the present analysis considers the bending stiffness of the core and also the transverse shear deformations of the laminated faces, the proposed method showed higher than that calculated according to the general laminated plates theory. The information presented might be useful to design sandwich plates structure with polymer matrix composite faces.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 춘계학술발표대회 논문집
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• pp.176-179
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• 2003

This paper deals with the optimum design of thick-walled multi-layered composite tubes by minimizing the process-induced residual stresses under some constraints of structural stiffnesses. An analytic model based on quasi-static thermoelasticity is adopted for the calculation of the residual stresses in the multi-layered composite tubes. The numerical results of optimization show that, in the case of cross-ply CFRP tubes, the residual stresses can be reduced to a certain level by controlling ply thicknesses. However, the optimized tubes may be susceptible to cracking because the transverse residual stress is still large in a strength-based sense. To further suppress the residual stresses, the effects of stacking sequence, wall thickness and axial pretension on the optimum solutions are examined.