• Title/Summary/Keyword: elastic composites

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A Study of damage behaviors of 3D orthogonal woven composite plates under Low velocity Impact (3D 직교 직물 복합재료 평판의 미시구조를 고려한 손상 거동 연구)

  • Ji, Kuk-Hyun;Yang, Jeong-Sik;Kim, Seung-Jo
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2005.11a
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    • pp.53-56
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    • 2005
  • In this study, the material characterization and the dynamic behavior of 3D orthogonal woven composite materials has been studied under transverse central low-velocity impact condition by means of the micromechanical model using finite elements. To build up the micromechanical model considering tow spacing and waviness, an accurate unit structure is stacked in x-y-z direction repeatedly. First, the mechanical properties of 3D orthogonal woven composites arc obtained by means of virtual experiment using full scale Finite Element Analysis based on the DNS concepts, and the computed elastic properties arc validated by comparison to available experimental results. Second, using the implementation of this validated micromechanical model, 3D transient finite-clement analysis is performed considering contact and impact, and the impact behavior of 3D orthogonal woven composite is investigated. A comparison study with the homogenized model will be carried out in terms of global and local behaviors.

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Theoretical Study on the Strengthening Mechanism in Short Fiber Composites (단섬유 복합강화 메커니즘에 관한 이론적 연구)

  • 김홍건;최창용;노홍길
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2003.10a
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    • pp.295-300
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    • 2003
  • In discontinuous composite mechanics, shear lag theory is one of the most popular model because of its simplicity and accuracy. However, it does not provide sufficiently accurate strengthening predictions in elastic regime when the fiber aspect ratio is small. This is due to its neglect of stress transfer across the fiber ends and the stress concentrations that exist in the matrix regions near the fiber ends. To overcome this shortcoming, a more simplified shear lag model introducing the stress concentration factor which is a major function of modulus ratio is proposed. It is found that the proposed model gives a good agreement with finite element results and has the capability to correctly predict the values of intefacial shear stresses and local stress variations in the small fiber aspect ratio regime.

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A Study on the Optimal Design of Laminated Composites using Genetic Algorithm (유전자 알고리즘을 이용한 적층복합재료의 최적설계에 관한 연구)

  • 조석수;주원식;장득열
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1996.04a
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    • pp.729-737
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    • 1996
  • Laminated composite plates have been applied to aircraft structures because their properties are superior to the conventional materials and the laminates have anisortropic elastic properties. However, it tis diffcult to determine stacking structures using actual design variables for the lack of searching capability of existing optimization technique. GA(generic algorithms) are robust search algorithms based on the mechanics of natural selection and natural genetics. Therefore, this study presents an application of IGA to stiffness and weight optimization design and gives the various stacking structures suitable to constraint conditions.

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Researches on the Enhancement of Plasticity of Bulk Metallic Glass Alloys

  • Kim, Byoung Jin;Kim, Won Tae
    • Applied Microscopy
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    • v.45 no.2
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    • pp.52-57
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    • 2015
  • Bulk metallic glass (BMG) shows higth strength, high elastic limit, corrosion resistance and good wear resistance and soft magnetic properties and has been considering as a candidate for new structural materials. But they show limited macroscopic plasticity and lack of tensile ductility due to highly localized shear deformation, which should be solved for real structural application. In this paper researches on the enhancement of plasticity of BMG were reviewed briefly. Introducing heterogeneous structure in glass is effective to induce more shear transformation zones (STZs) active for multiple shear band initiation and also to block the propagating shear band. Several methods such as BMG alloy design for high Poisson's ratio, addition of alloying element having positive heat of mixing, pre-straining BMG and variety of BMG composites have been developed for homogenous distribution of locally weak region, where local strain can be initiated. Therefore enhancement of plasticity of BMG is normally accompanied with some penalty of strength loss.

Multifield Variational Finite Element Sectional Analysis of Composite Beams

  • Dhadwal, Manoj Kumar;Jung, Sung Nam
    • Composites Research
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    • v.30 no.6
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    • pp.343-349
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    • 2017
  • A multifield variational formulation is developed for the finite element (FE) cross-sectional analysis of composite beams. The cross-sectional warping displacements and sectional stresses are considered to be the primary variables through the application of Reissner's partially mixed principle. The warping displacements are modeled using generic FE shape functions with nonlinear distribution over the beam section. A generalized Timoshenko level stiffness matrix is derived which incorporates the effects of elastic couplings, transverse shear, and Poisson's deformations. The accuracy of the present analysis is validated for the stiffness constants and elastostatic responses of composite box beams which correlate well with the experimental data and other state-of-the-art approaches.

Compression strength of pultruded equal leg angle sections

  • Polyzois, D.;Raftoyiannis, I.G.
    • Structural Engineering and Mechanics
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    • v.9 no.6
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    • pp.541-555
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    • 2000
  • Pultruded cross-sections are always thin-walled due to constraints in the manufacturing process. Thus, the buckling strength determines the overall strength of the member. The elastic buckling of pultruded angle sections subjected to direct compression is studied. The lateral-torsional buckling, very likely to appear in thin-walled cross-sections, is investigated. Plate theory is used to allow for cross-sectional distortion. Shear effects and bending-twisting coupling are accounted for in the analysis because of their significant role. A simplified approach for determining the maximum load of equal leg angle sections under compression is presented. The analytical results obtained in this study are compared to the manufacturer's design guidelines for compression members as well as with the design specifications for steel structural members. Experimental results are obtained for various length specimens of pultruded angle sections. The results presented in this paper correspond to actual pultruded equal leg angle sections being used in civil engineering structures.

Natural Frequency of Elastic Supported Building Slab (탄성지지된 복합재료 상판의 고유 진동수)

  • 김덕현;이정호;박정호
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1997.10a
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    • pp.215-222
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    • 1997
  • A method of calculating the natural frequency corresponding to the first mode of vibration of beams and tower structures, with irregular cross-sections and with arbitrary boundary conditions was developed and reported by D. H. Kim in 1974. This method has been developed for two-dimensional problems including the laminated composite plates and was proved to be very effective for the plates with arbitrary boundary conditions and irregular sections. In this paper, the result of application of this method to the subject problem is presented. This problem represents the building slabs with a kind of passive and active control devices. Any method may be used to obtain the deflection influence surfaces needed for this vibration analysis. Finite difference method is used for this purpose, in this paper. The influence of the modulus of the foundation on the natural frequency is thoroughly studied.

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Transverse Flow and Process Modeling on the Polymer Composite with 3-Dimensionally Stitched Woven Fabric

  • Lee, Geon-Woong;Lee, Sang-Soo;Park, Min;Kim, Junkyung;Soonho Lim
    • Macromolecular Research
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    • v.10 no.4
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    • pp.194-203
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    • 2002
  • In resin infusion process(RIP), the fiber and the resin are in contact with each other for an impregnation step and often results in flow-induced defects such as poor fiber wetting and void formation. Resin flow characteristics in transverse direction and process modeling for woven fabric were studied, and the process modeling was applied to the manufacturing of hybrid composite materials. This study also considered the compressibility of woven fabrics in a series of compression force, and it was fitted well to an elastic model equation. Void formation was varied with the processing conditions in the stage of manufacturing composites using RIP. It was concluded from this study that proper combination of pressure build-up and dynamic heating condition makes important factor for flow-induced composite processing.

Tribological Behavior of Silicon Carbide Ceramics - A Review

  • Sharma, Sandan Kumar;Kumar, B. Venkata Manoj;Kim, Young-Wook
    • Journal of the Korean Ceramic Society
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    • v.53 no.6
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    • pp.581-596
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    • 2016
  • A comprehensive review on sliding and solid particle erosion wear characteristics of silicon carbide (SiC) ceramics and SiC composites is provided. Sliding or erosion wear behavior of ceramics is dependent on various material characteristics as well as test parameters. Effects of microstructural and mechanical properties of SiC ceramics are particularly focused to understand tribological performance of SiC ceramics. Results obtained between varieties of pairs of SiC ceramics indicate complexity in understanding dominant mechanisms of material removal. Wear mechanisms during sliding are mainly divided in two groups as mechanical and tribochemical. In solid particle erosion conditions, wear mechanisms of SiC ceramics are explained by elastic-plastic deformation controlled micro-fracture on the surface followed by radial-lateral crack propagation beneath the plastic zone.

A simple plane-strain solution for functionally graded multilayered isotropic cylinders

  • Pan, E.;Roy, A.K.
    • Structural Engineering and Mechanics
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    • v.24 no.6
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    • pp.727-740
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    • 2006
  • A simple plane-strain solution is derived in this paper for the functionally graded multilayered isotropic elastic cylinder under static deformation. The solution is obtained using method of separation of variables and is expressed in terms of the summation of the Fourier series in the circumferential direction. While the solution for order n = 0 corresponds to the axisymmetric deformation, that for n = 2 includes the special deformation frequently utilized in the upper and lower bounds analysis. Numerical results for a three-phase cylinder with a middle functionally graded layer are presented for both axisymmetric (n = 0) and general (n = 2) deformations, under either the traction or displacement boundary conditions on the surface of the layered cylinder. The solution to the general deformation case (n = 2) is further utilized for the first time to find the upper and lower bounds of the effective shear modulus of the layered cylinder with a functionally graded middle layer. These results could be useful in the future study of cylindrical composites where FGMs and/or multilayers are involved.