• Title/Summary/Keyword: Interlaminar Stress

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Stress Function-Based Interlaminar Stress Analysis of Composite Laminates under Complex Loading Conditions (응력함수에 기초한 복합 하중하의 복합재 적층판의 층간응력 해석)

  • Kim, H.S.;Kim, J.Y.;Kim, J.G.
    • Journal of Power System Engineering
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    • v.14 no.3
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    • pp.52-57
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    • 2010
  • Interlaminar stresses near the free edges of composite laminates have been analyzed considering wall effects. Interface modeling of bonding layer was introduced to explain the wall effect. Using Lekhnitskii stress functions and the principle of complementary virtual work, the interlaminar stresses were obtained, which satisfied the traction free boundary conditions not only at the free edges, but also at the top and bottom surfaces of laminates. The interface modeling provides not singular stresses but concentrated finite interlaminar stresses. The significant amount of reductions of stresses at the free edge are observed compared to the results without interface modeling. The real stress state can be predicted accurately and the results demonstrate the usefulness of the proposed interface modeling for the strength design of composite laminates.

Interlaminar Normal Stress Effects in Cylindrical Tubular Specimens of Graphite/Epoxy [±45]s Composites

  • An, Deuk Man
    • Composites Research
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    • v.30 no.6
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    • pp.406-409
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    • 2017
  • The thin-walled cylindrical tubes are frequently used for the evaluation of fatigue property of composites. But the curvature of the tubular specimen induces interlaminar normal stress which may affect the fatigue property. In this paper interlaminar normal stress effect on the fatigue behaviour of thin-walled graphite/epoxy tubes $[{\pm}45]_s$ composites was studied experimentally. It was concluded that the interlaminar normal stress induced by the curvature of the cylinder has no discernible effect on the fatigue life. But excessive internal pressure can produce the stiffness increase and this affects the fatigue life of the cylindrical tubular composite.

Interlaminar stress behavior of laminated composite plates under Low velocity Impact (저속충격을 받는 적층복합재료 평판의 미시구조를 고려한 interlaminar stress 거동 연구)

  • Ji, Kuk-Hyun;Kim, Seung-Jo
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2005.04a
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    • pp.249-252
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    • 2005
  • Prediction of damage caused by low-velocity impact in laminated composite plate is an important problem faced by designers using composites. Not only the inplane stresses but also the interlaminar normal and shear stresses playa role in estimating the damage caused. The work reported here is an effort in getting better predictions of damage in composite plate using DNS approach. In the DNS model, we discretize the composite plates through separate modeling of fiber and matrix for the local microscopic analysis. Through comparison with the homogenized model. In the view of microscopic mechanics with DNS model, interlaminar stress behaviors in the inside of composite materials is investigated and compared with the results of the homogenized model which has been used in the conventional approach of impact analysis.

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3D Non-linear Analysis of Interlaminar Stress around the Hole Edge of Orthotropic Laminates (직교이방성 적층판의 Hole단부의 3D 비선형 층간응력 해석)

  • SONG KWAN-HYUNG
    • Journal of Ocean Engineering and Technology
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    • v.18 no.5
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    • pp.36-42
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    • 2004
  • Orthotropic laminates, such as [$0^{\circ}6$/$90^{\circ}6$]s and [$90^{\circ}6$/$0^{\circ}6$]s, were performed, using a commercial nonlinear finite element method. Interlaminar stress distributions, around the hole curve free-edge, were calculated. The delamination bearing strengths of pin joints were predicted, using the modified delamination failure criterion. These stress distributions were presented along the radial lines and around the free-edge of the hole. Further, three-dimensional non-linear contact analysis of orthotropic laminates was conducted to investigate the effect of friction. In this paper, laminates with a circular hole were taken to study interlaminar stresses the curved edge. This study may assist in the design of a thick composite laminate with mechanically pin joints.

Thermal Stresses in a Laminated Fiber-Reinforced Composite Containing an Interlaminar Crack Under a Uniform Heat Flow (층간균열이 존재하는 균일 열유동하의 섬유강화 적층복합재료의 열응력해석)

  • 최형집;오준성;이강용
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.4
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    • pp.887-902
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    • 1994
  • Within the framework of anisotropic thermoelasticity, the problem of an interlaminar crack in a laminated fiber-reinforced composite subjected to a uniform heat flow is investigated. Under a state of generalized plane deformation, dissimilar anisotropic half-spaces with different fiber orientations are considered to be bound together by a matrix interlayer containing the crack. The interlayer models the matrix-rich interlaminar region of the fibrous composite laminate. Based on the flexibility/stiffness matrix approach, formulation of the current crack problem results in having to solve two sets of singular integral equations for temperature and thermal stress analyses. Numerical results are obtained, illustrating the parametric effects of laminate stacking sequence, relative crack size, crack location, crack surface partial insulation, and fiber volume fraction on the values of mixed mode thermal stress intensity factors.

Interlaminar stresses and delamination of composite laminates under extension and bending

  • Nguyen, Tien Duong;Nguyen, Dang Hung
    • Structural Engineering and Mechanics
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    • v.25 no.6
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    • pp.733-751
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    • 2007
  • The metis element method (Hung 1978) has been applied to analyse free edge interlaminar stresses and delamination in composite laminates, which are subjected to extension and bending. The paper recalls Lekhnitskii's solution for generalized plane strain state of composite laminate and Wang's singular solution for determination of stress singularity order and of eigen coefficients $C_m$ for delamination problem. Then the formulae of metis displacement finite element in two-dimensional problem are established. Computation of the stress intensity factors and the energy release rates are presented in details. The energy release rate, G, is computed by Irwin's virtual crack technique using metis elements. Finally, results of interlaminar stresses, the three stress intensity factors and the energy release rates for delamination crack in composite laminates under extension and bending are illustrated and compared with the literature to demonstrate the efficiency of the present method.

Experimental Evaluation of Fatigue Behavior and Interlaminar Phase in the Lightweight Piezoelectric Ceramic Composite Actuator Using the Ultrasonic C-scan Inspection (초음파 C-스캔 탐상을 이용한 경량 압전세라믹 복합재료 작동기의 피로거동과 계면변화의 관계 연구)

  • Kim Cheol-Woong;Nam In-Chang;Yoon Kwang-Joon
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.06a
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    • pp.1332-1336
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    • 2005
  • It could make the LIghtweight Piezoelectric Composite Actuator (LIPCA) damageable by the cyclic large deformation. If the progressive microvoid coalescence of LIPCA interlaminar took place, the decrease of the stiffness and the weakness of stress transmission and fiber bridging effect would make the fatigue characteristics worse suddenly. Therefore, it is required to study the variation of fatigue behavior and interlaminar condition in LIPCA under resonant frequencies. These studies such as the changeable fatigue phase and interlaminar behavior of LIPCA affected by the resonant frequencies should be carried out due to the strong anisotropy of CFRP layer. Hence, these studies are as follows. 1) The residual stresses distribution of interlaminar in LIPCA using the Classical Lamination Theory (CLT). 2) Comparative analysis of interlaminar behavior for the intact LIPCA versus LIPCA containing an artificial delamination during resonant frequency.

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Interlaminar Shear Stresses of Laminated Composite Plates Subjected to Transversely Imp (횡방향 충격을 받는 적층복합판의 층간전단응력 해석)

  • Ahn, Kook-Chan;Park, Seung-Bum;Kim, Bong-Hwan
    • Journal of the Korean Society of Safety
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    • v.17 no.4
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    • pp.31-37
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    • 2002
  • This paper demonstrates the analyses of the interlaminar shear stress of laminated composite plates subjected to transversely impact. For this purpose, a plate finite element model based on the higher order shear deformation plate theory in conjunction with static contact laws is developed. Test materials were CFRP with cross-ply laminate $[O_4/{\theta}_4]_S$, $[90_4/{\theta}_4]_S$ stacking sequences and angle-ply laminate $[{\theta}_4/-{\theta}_4]_S$, $[{\theta}_4/-{\theta}_4]_S$ stacking deguences with $2^t{\times}40^w{\times}100^l(mm)$ dimension. As a result, stacking seguence and fiber orientation were found to have a significant effect on the interlaminar stresses in composite laminates.

Enhancing Structural Integrity of Composite Sandwich Beams Using Viscoelastic Bonding with Tapered Epoxy Reinforcement

  • Rajesh Lalsing Shirale;Surekha Anil Bhalchandra
    • Korean Journal of Materials Research
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    • v.34 no.3
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    • pp.125-137
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    • 2024
  • Composite laminates are used in a wide range of applications including defense, automotive, aviation and aerospace, marine, wind energy, and recreational sporting goods. These composite beams still exhibit problems such as buckling, local deformations, and interlaminar delamination. To overcome these drawbacks, a novel viscoelastic autoclave bonding with tapered epoxy reinforcement polyurethane films is proposed. In existing laminates, compression face wrinkling and interlaminar delamination is caused in the sandwich beam. The unique viscoelastic autoclave spunbond interlayer bonding is designed to prevent face wrinkling and absorb and distribute stresses induced by external loads, thereby eliminating interlaminar delamination in the sandwich beam. Also, the existing special reinforcement causes stress concentrations, and the core is not effectively connected, which directly affects the stiffness of the beam. To address this, a novel tapered epoxy polyurethane reinforcement adhesive film is proposed, whose reinforcement thickness gradually tapers as it enters the core material. This minimizes stress concentrations at the interface, preventing excessive adhesive squeeze-out during the bonding process, and improves the stiffness of the beam. Results indicate the proposed model avoids the formation of micro cracks, interlaminar delamination, buckling, and local deformations, and effectively improves the stiffness of the beam.

Response of dynamic interlaminar stresses in laminated plates under free vibration and thermal load

  • Zhu, S.Q.;Chen, X.;Wang, X.
    • Structural Engineering and Mechanics
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    • v.25 no.6
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    • pp.753-765
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    • 2007
  • The response histories and distribution of dynamic interlaminar stresses in composite laminated plates under free vibration and thermal load is studied based on a thermoelastodynamic differential equations. The stacking sequence of the laminated plates may be arbitrary. The temperature change is considered as a linear function of coordinates in planes of each layer. The dynamic mode of displacements is considered as triangle series. The in-plane stresses are calculated by using geometric equations and generalized Hooke's law. The interlaminar stresses are evaluated by integrating the 3-D equations of equilibrium, and utilizing given boundary conditions and continuity conditions of stresses between layers. The response histories and distribution of interlaminar stress under thermal load are presented for various vibration modes and stacking sequence. The theoretical analyses and results are of certain significance in practical engineering application.