• Title, Summary, Keyword: Orthotropic Composites

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Effects of Anisotropic Fiber Packing on Stresses in Composites (이방성 섬유의 배열이 복합재료의 응력에 미치는 영향)

  • Lee, Jung-Ki;Lee, Hyeong-Min
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.9
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    • pp.1284-1296
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    • 2004
  • In order to investigate effects of anisotropic fiber packing on stresses in composites, a Volume Integral Equation Method is applied to calculate the elastostatic field in an unbounded isotropic elastic medium containing multiple orthotropic inclusions subject to remote loading, and a Mixed Volume and Boundary Integral Equation Method is introduced for the solution of elastostatic problems in unbounded isotropic materials containing multiple anisotropic inclusions as well as one void under uniform remote loading. A detailed analysis of stress fields at the interface between the isotropic matrix and the central orthotropic inclusion is carried out for square, hexagonal and random packing of orthotropic cylindrical inclusions, respectively. Also, an analysis of stress fields at the interface between the isotropic matrix and the central orthotropic inclusion is carried out, when it is assumed that a void is replaced with one inclusion adjacent to the central inclusion of square, hexagonal and random packing of orthotropic cylindrical inclusions, respectively, due to manufacturing and/or service induced defects. The effects of random orthotropic fiber packing on stresses at the interface between the isotropic matrix and the central orthotropic inclusion are compared with the influences of square and hexagonal orthotropic fiber packing on stresses. Through the analysis of plane elastostatic problems in unbounded isotropic matrix with multiple orthotropic inclusions and one void, it will be established that these new methods are very accurate and effective for investigating effects of general anisotropic fiber packing on stresses in composites.

Nonlinear Anisotropic Hardening Laws for Orthotropic Fiber-Reinforced Composites (직교이방 섬유강화 복합재료의 비선형 비등방 경화법칙)

  • 김대용;이명규;정관수
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.75-78
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    • 2003
  • In order to describe the Bauschinger and transient behavior of orthotropic fiber-reinforced composites, a combined isotropic-kinematic hardening law based on the non-linear kinematic hardening rule was considered here, in particular, based on the Chaboche type law. In this modified constitutive law, the anisotropic evolution of the back-stress was properly accounted for. Also, to represent the orthotropy of composite materials, Hill's 1948 quadratic yield function and the orthotropic elasticity constitutive equations were utilized. Furthermore, the numerical formulation to update the stresses was also developed based on the incremental deformation theory for the boundary value problems. Numerical examples confirmed that the new law based on the anisotropic evolution of the back-stress complies well with the constitutive behavior of highly anisotropic materials such as fiber-reinforced composites.

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Effect of element size in hybrid stress analysis around a hole in loaded orthotropic composites (직교이방성 재료의 구멍주위에 관한 하이브리드 응력해석시 요소크기의 효과)

  • Baek, Tae-Hyun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.10
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    • pp.1702-1711
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    • 1997
  • A numerical study for the number of terms of a power series stress function and the effect of hybrid element size on stress analysis around a hole in loaded orthotropic composites is presented. The hybrid method coupling experimental and/or theoretical inputs and complex variable formulations involving conformal mappings and analytical continuity is used to calculate tangential stress on the boundary of the hole in uniaxially loaded, finite width glass epoxy tensile plate. The tests are done by rarying the number of terms, element size and nodal locations on the external boundary of the hybrid region. The numerical results indicate that the hybrid method is accurate and powerful in both experimental and numerical stress analysis.

A Study on Characteristics Analysis of Low Velocity Impact Response of CF/Epoxy Composite Plates (CF/Epoxy 복합적층판의 저속충격 특성평가에 관한 연구)

  • 임광희;박노식;김영남;김정호;김선규;심재기;양인영
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.85-88
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    • 2002
  • We have implemented a system of falling weight impact tester. Absorbed energy of orthotropic composites with using T300 fiber, which are composed of the same fiber and stacking number is higher than that of quasi-isotropic specimen over impact energy 7J, but in case of using T700 fiber, much difference does not show. Also, absorbed energy of orthotropic composites with using T300 fiber, which are composed of stacking number and orientation became more than that of T700 fiber specimen; however great change doesn't show in case of quasi-isotropic specimens. Delamination area of impacted specimens was measured with ultrasonic C-scanner to find correlation between impact energy and delamination area. Delamination area and frequency responses was evaluated between impacted and unimpacted specimens. There is a strong correlation between frequency responses and impact-induced delamination. The presence and scale of damages have been investigated based on the variations of frequency responses.

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A study on the dynamic characteristics of the cord-rubber laminates rectangular plate by finite element method (유한요소법을 이용한 코오드-고무 복합판의 동적특성에 관한 연구)

  • 김두만;김항욱
    • Journal of the korean Society of Automotive Engineers
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    • v.8 no.2
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    • pp.51-64
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    • 1986
  • There has been considerable interest over the last twenty years in the subject of the elastic properties of the cord-rubber laminate. This has been due to the rather intensive study of the composites materials characteristics brought about by the increased use of rigid composites materials characteristics brought about by the increased use of rigid composites in many structural applications. The object of this study is to obtain the natural frequencies and modes of the simply supported cord-rubber laminate plates prior to the study on the analysis of the dynamic properties of the pneumatic tire. To obtain these natural frequencies and modes, the 12 degrees of freedom orthotropic rectangular plate finite elements are developed. By using classical lamination theory, the stress-strain relations are represented. The governing equation for the finite element is derived by energy method. To find the natural frequencies and modes, he eigenvalues and corresponding eigenvectors are computed by the well known Jacobi power method. In order to verify the capability of this present finite element, the results of the specially orthotropic plate and the angle-ply laminate plate are compared with the analytical solution. The analytical and numberical results are in good agreement. The following problems of the simply supported plate are analyzed by the present finite element. a) the natural frequencies and mode shapes of the cord-rubber laminate plate for various aspect ratio. b) The natural frequencies and mode shapes of the orthotropic plate with the rectangular hole in its center.

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Manufacturing Functional Nano-Composites by Using Field-Aided Micro-Tailoring Manipulation (Field-Aided Micro-Tailoring에 의한 기능성 나노복합재 제조)

  • Cho, Hee-Keun;Rhee, Juhun;Sim, Eun-Sup
    • Composites Research
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    • v.25 no.6
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    • pp.178-185
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    • 2012
  • One of a unique technique in manipulating a multifunctional composite is demonstrated in this study. An electric field is applied to a liquid suspension in order to align the inclusions along with the direction electric field. This is called FAiMTa(Field Aided Micro Tailoring). It makes orthotropic polymer composites by arranging the micro and/or nano size particle inclusions in chain-line formation. Several kinds of particles such as $Al_2O_3$, graphite, CNT(Carbon Nano Tube), W(Tungsten) are tested to verify the effectiveness of the FAiMTa. The particles redistributed in an epoxy suspension and their coupons show that mechanical and thermal properties of orthotropic and random composites containing those particles depend on the trend of particles' alignment. The micro-images of the functional composite from FAiMTa have been captures and their physical properties demonstrate their wide-range and state-of-the-art application for advanced multifunctional composites.

Analysis of Post-tensioned Bridge by Specially Orthotropic Laminate Theory (I) - Reinforced Concrete Slab Bridge (특별직교이방성 이론에 의한 포스트 텐션된 교량의 해석(I) - 철근 콘크리트 슬래브교 -)

  • 김덕현;원치문;이정호
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.135-140
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    • 2001
  • A post-tensioned reinforced concrete slab bridge is analyzed by specially orthotropic laminate theory. Symmetrically reinforced slab with tension and compression steel is considered for convenience of analysis. Each longitudinal and transverse steel layer is regarded as a lamina, and material constants of each lamina is calculated by the use of the rule of mixture. This bridge is under uniformly distributed vertical loads, and axial loads and end moments due to post-tensioning. In this paper, finite difference method is used for numerical analysis of this bridge. Theory and analysis method of specially orthotropic laminate plates used in this paper can be used for design of new bridges, and maintenance and repair of old bridges.

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Analysis of Post-tensioned Bridge by Specially Orthotropic Laminate Theory (II) - Steel Plate Girder Bridge (특별직교이방성 이론에 의한 포스트 텐션된 교량의 해석(II) - 강 판형교 -)

  • 김덕현;원치문;이정호
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.141-146
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    • 2001
  • A post-tensioned steel plate girder bridge with cross-beams is analyzed by specially orthotropic laminate theory. The cross-sections of both girders and cross-beams are WF types. The result is compared with that of the beam theory. This bridge with simple support is under uniformly distributed vertical load, and axial loads and moment due to post-tension. In this paper, finite difference method for numerical analysis of simple supported bridge is developed. Relatively exact solution is obtained even with small number of meshes. Theory and analysis method of specially orthotropic laminate plates used in this paper can be used in design of new bridges, and maintenance and repair of old bridges.

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The Study on Axisymmetric Deformation of Thin Orthotropic Composite Pressure Vessel (직교이방성 복합재료로 만든 두께가 얇은 압력용기의 변형에 관한 연구)

  • 김형원;최용규
    • Journal of the Korean Society of Propulsion Engineers
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    • v.7 no.2
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    • pp.36-43
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    • 2003
  • The analytic solution of radial displacements of thin cylindrical pressure vessel with carbon fiber T700/Epoxy orthotropic composites was obtained using equilibrium equations of the orthogonal curvilinear coordinate system. The governing equations with the simplified strain versus displacement relation of 3-dimensional curvilinear coordinate system were derived from the variational principle and the virtual work principle. Some theoretical analyses were presented and compared with the results of hydraulic tests for the pressure vessels with some various thicknesses. The results of the theoretical analysis and the hydraulic test were reasonably matched.

A Simple Method of Vibration Analysis of Speical Orthotropic Plate with A Pair of Opposite Edges Simply Supported and the Other Pair of Opposite Edges Free (양단단순-타단자유인 특별직교이방성 적층복합판의 간편한 진동해석)

  • 김덕현;이정호;홍창우;박제선
    • Composites Research
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    • v.12 no.4
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    • pp.33-41
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    • 1999
  • In this paper, a simple but accurate method of vibration analysis of structural elements with or without attached mass/masses is presented. The method used has been developed by D.H., Kim since 1974. This method is very effective for the plates with arbitrary conditions and irregular sections. This method is applied to the special orthotropic plate with two opposite edges simply supported and the other two opposite edges free. Such plate represents the most of the simply supported bridges/decks, including concrete and girders-cross beam systems. Detailed illustration is given for beams and plates for easy understanding. Some laminate orientation for which the special orthotropic equations can be applied are identified.

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