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M. Shariyat - One of the best experts on this subject based on the ideXlab platform.
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A general nonlinear global-local theory for bending and buckling analyses of imperfect cylindrical laminated and sandwich shells under thermomechanical loads
Meccanica, 2012Co-Authors: M. ShariyatAbstract:The accurate shell theories proposed so far have been calibrated based on linear kinematic relations. Many of them have ignored either the interlaminar Stress Continuity conditions at the interfaces or the transverse flexibility of the layers. Therefore, the available shell theories may encounter accuracy problems when analyzing the nonlinear behaviors, especially for sandwich shells with soft cores. Moreover, almost all of the available shell theories have been proposed employing the Love-Timoshenko assumption. Ideas of the previous global-local plate theory of the author are extended to develop the present nonlinear high-order global-local shell theory. The present theory has the advantages of: (1) suitability for non-linear analyses, (2) higher accuracy due to satisfying the complete interlaminar kinematic and transverse Stress Continuity conditions at the layer interfaces under thermo-mechanical loads, employing the exact Green’s strain tensor of the curvilinear coordinates, considering the transverse flexibility, and releasing the Love-Timoshenko assumption, (3) less required computational time due to using the global-local technique and matrix formulations, and (4) capability of investigating the local phenomena. To enhance the accuracy of the results, compatible Hermitian elements are employed. Various comparative examples are included in the present paper to validate the theory and to examine its accuracy and efficiency.
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an accurate double superposition global local theory for vibration and bending analyses of cylindrical composite and sandwich shells subjected to thermo mechanical loads
Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2011Co-Authors: M. ShariyatAbstract:Based on the idea of double superposition, an accurate high-order global–local theoryis proposed for bending and vibration analysis of cylindrical shells subjected to thermo-mechanical loads, for the first time. The theory has many novelties, among them: (1) less computational time due to the use of the global–local technique and matrix formulations; (2) satisfaction of the complete kinematic and transverse Stress Continuity conditions at the layer interfaces under thermo-mechanical loads; (3) consideration of the transverse flexibility; (4) release of Love–Timoshenko assumption; and (5) capability of investigating the local phenomena. Various comparative examples are included to validate the theory and to examine its accuracy and efficiency.
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a nonlinear double superposition global local theory for dynamic buckling of imperfect viscoelastic composite sandwich plates a hierarchical constitutive model
Composite Structures, 2011Co-Authors: M. ShariyatAbstract:Abstract Nonlinear dynamic thermo-mechanical buckling and postbuckling analyses of imperfect viscoelastic composite laminated/sandwich plates are performed by a proposed theory that takes into account all the interlaminar kinematic and transverse Stress Continuity conditions, for the first time. Even the dynamic buckling analysis of the multi-layered/sandwich plates employing the hierarchical constitutive model has not been performed before. The proposed theory is a double-superposition high-order global–local theory that is calibrated based on the nonlinear strain–displacement expressions for the thermoelastic loadings taking into account the structural damping. The buckling loads are determined based on a criterion previously published by the author. Various complex sensitivity analyses evaluating effects of the relaxation parameters, rate of the loading, sudden heating, and pre-Stress on thermo-mechanical buckling of the viscoelatic multi-layered/sandwich plates are performed. Results show that the viscoelastic behavior may decrease the buckling load. Sudden dynamic buckling loads are higher due to the reflected Stress waves.
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a generalized global local high order theory for bending and vibration analyses of sandwich plates subjected to thermo mechanical loads
International Journal of Mechanical Sciences, 2010Co-Authors: M. ShariyatAbstract:Abstract Although the global higher-order shear deformation theories may predict the gross responses of the sandwich plates sufficiently accurate, their results may show considerable errors in predicting the local effects. Layerwise and mixed layerwise theories are computationally expensive and generally, the interlaminar transverse Stresses Continuity conditions are not enforced in the former category of theories. Majority of the available zigzag and global–local theories suffer from the point that the transverse normal Stress Continuity that influences the transverse deformation significantly, especially in sandwich plates with soft-cores, is not satisfied at the layer interfaces. In the present paper, a generalized global–local theory that guarantees the Continuity condition of all of the displacement and transverse Stress components and considers the transverse flexibility under thermo-mechanical loads is introduced. One of the advantages of the present theory is that the number of unknown parameters is independent of the number of the layers. Furthermore, all Stress components are considered in the formulations. Therefore, in contrast to the available works, the theory may be used for sandwich plates with stiff or soft cores. In contrast to the available global–local formulations, the present formulation is developed in a compact matrix form that makes it more desirable for computerized solutions. The present theory may be considered as a generalized layerwise theory with an optimized computational time. Compatible quadrilateral Hermitian elements are employed to further enhance the accuracy of the results. Validity, advantages, and efficiency of the present theory are investigated for different local and global behaviors of the layered composite and sandwich plates. Comparison of the present results with those of the three-dimensional theory of elasticity and the available plate theories confirms the efficiency and accuracy of the proposed theory. Results reveal that the global theories (e.g. the higher-order shear deformation theories) may encounter serious accuracy problems even in predicting the gross responses of the sandwich plates.
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non linear dynamic thermo mechanical buckling analysis of the imperfect sandwich plates based on a generalized three dimensional high order global local plate theory
Composite Structures, 2010Co-Authors: M. ShariyatAbstract:Abstract The available plate theories either have not considered the interlaminar Stress Continuity condition or have been calibrated based on linear strain–displacement relations. Moreover, almost all buckling analyses performed so far employing the global–local plate theories, were restricted to linear, static buckling analyses of the perfect plates, neglecting the transverse normal strain and Stress. Researches available in literature for dynamic buckling analyses of the sandwich plates are very rare. In the present paper, a generalized high-order global–local theory that satisfies all the kinematic and transverse Stress Continuity conditions at the interfaces of the layers, is proposed to investigate dynamic buckling of imperfect sandwich plates subjected to thermo-mechanical loads. In comparison to the layerwise, mixed, and available global–local theories, the present theory has the advantages of: (1) less required computational time due to using the global–local technique and matrix formulations, (2) higher accuracy due to satisfying the complete interlaminar kinematic and transverse Stress Continuity conditions and considering the transverse flexibility, (3) suitability for non-linear analyses, (4) capability of investigating the local phenomena, such as the wrinkling. To enhance the accuracy of the results, compatible Hermitian quadrilateral elements are employed. The buckling loads are determined based on a criterion previously published by the author.
Chen Wanji - One of the best experts on this subject based on the ideXlab platform.
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an accurate higher order theory and c0 finite element for free vibration analysis of laminated composite and sandwich plates
Composite Structures, 2010Co-Authors: Wu Zhen, Chen Wanji, Ren XiaohuiAbstract:Abstract At present, it is difficult to accurately predict natural frequencies of sandwich plates with soft core by using the C 0 plate bending elements. Thus, the C 1 plate bending elements have to be employed to predict accurately dynamic response of such structures. This paper proposes an accurate higher-order C 0 theory which is very different from other published higher-order theory satisfying the interlaminar Stress Continuity, as the first derivative of transverse displacement has been taken out from the in-plane displacement fields of the present theory. Therefore, the C 0 interpolation functions is only required during its finite element implementation. Based on the Hamilton’s principle and Navier’s technique, analytical solutions to the natural frequency analysis of simply-supported laminated plates have been presented. To further extend the ranges of application of the proposed theory, an eight-node C 0 continuous isoparametric element is used to model the proposed theory. Numerical results show the present C 0 finite element can accurately predict the natural frequencies of sandwich plate with soft core, whereas other global higher-order theories are unsuitable for free vibration analysis of such soft-core structures.
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a global local higher order theory including interlaminar Stress Continuity and c0 plate bending element for cross ply laminated composite plates
Computational Mechanics, 2010Co-Authors: Wu Zhen, Chen WanjiAbstract:A C0-type global-local higher order theory including interlaminar Stress Continuity is proposed for the cross-ply laminated composite and sandwich plates in this paper, which is able to a priori satisfy the Continuity conditions of transverse shear Stresses at interfaces. Moreover, total number of unknowns involved in the model is independent of number of layers. Compared to other higher-order theories satisfying the Continuity conditions of transverse shear Stresses at interfaces, merit of the proposed model is that the first derivatives of transverse displacement w have been taken out from the in-plane displacement fields, so that the C0 interpolation functions is only required during its finite element implementation. To verify the present model, a C0 three-node triangular element is used for bending analysis of laminated composite and sandwich plates. It ought to be shown that all variables involved in present model are discretized by only using linear interpolation functions within an element. Numerical results show that the C0 plate element based on the present theory may accurately calculate transverse shear Stresses without any postprocessing, and the present results agree well with those obtained from the C1-type higher order theory. Compared with the C1 plate bending element, the present finite element is simple, convenient to use and accurate enough.
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an efficient higher order theory and finite element for laminated plates subjected to thermal loading
Composite Structures, 2006Co-Authors: Wu Zhen, Chen WanjiAbstract:In the present paper, the global–local higher-order theory is simply derived, which satisfies the free surface conditions and the geometric and Stress Continuity conditions at interfaces. Moreover, the number of unknowns of this theory is independent of the layer numbers of the laminate. Based on the global–local higher-order theory, the discrete Kirchhoff element PDKT and refined triangular plate element PRT9 are presented for predicting interlaminar Stresses and displacements in laminated plates subjected to thermal loading. The two triangular elements satisfy the interelement C1 Continuity conditions. The numerical examples show that the in-plane Stresses and transverse shear Stresses can be accurately calculated by the direct constitutive equation approach. The equilibrium equation approach is employed to predict transverse normal Stresses.
Wu Zhen - One of the best experts on this subject based on the ideXlab platform.
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an accurate higher order theory and c0 finite element for free vibration analysis of laminated composite and sandwich plates
Composite Structures, 2010Co-Authors: Wu Zhen, Chen Wanji, Ren XiaohuiAbstract:Abstract At present, it is difficult to accurately predict natural frequencies of sandwich plates with soft core by using the C 0 plate bending elements. Thus, the C 1 plate bending elements have to be employed to predict accurately dynamic response of such structures. This paper proposes an accurate higher-order C 0 theory which is very different from other published higher-order theory satisfying the interlaminar Stress Continuity, as the first derivative of transverse displacement has been taken out from the in-plane displacement fields of the present theory. Therefore, the C 0 interpolation functions is only required during its finite element implementation. Based on the Hamilton’s principle and Navier’s technique, analytical solutions to the natural frequency analysis of simply-supported laminated plates have been presented. To further extend the ranges of application of the proposed theory, an eight-node C 0 continuous isoparametric element is used to model the proposed theory. Numerical results show the present C 0 finite element can accurately predict the natural frequencies of sandwich plate with soft core, whereas other global higher-order theories are unsuitable for free vibration analysis of such soft-core structures.
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a global local higher order theory including interlaminar Stress Continuity and c0 plate bending element for cross ply laminated composite plates
Computational Mechanics, 2010Co-Authors: Wu Zhen, Chen WanjiAbstract:A C0-type global-local higher order theory including interlaminar Stress Continuity is proposed for the cross-ply laminated composite and sandwich plates in this paper, which is able to a priori satisfy the Continuity conditions of transverse shear Stresses at interfaces. Moreover, total number of unknowns involved in the model is independent of number of layers. Compared to other higher-order theories satisfying the Continuity conditions of transverse shear Stresses at interfaces, merit of the proposed model is that the first derivatives of transverse displacement w have been taken out from the in-plane displacement fields, so that the C0 interpolation functions is only required during its finite element implementation. To verify the present model, a C0 three-node triangular element is used for bending analysis of laminated composite and sandwich plates. It ought to be shown that all variables involved in present model are discretized by only using linear interpolation functions within an element. Numerical results show that the C0 plate element based on the present theory may accurately calculate transverse shear Stresses without any postprocessing, and the present results agree well with those obtained from the C1-type higher order theory. Compared with the C1 plate bending element, the present finite element is simple, convenient to use and accurate enough.
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an efficient higher order theory and finite element for laminated plates subjected to thermal loading
Composite Structures, 2006Co-Authors: Wu Zhen, Chen WanjiAbstract:In the present paper, the global–local higher-order theory is simply derived, which satisfies the free surface conditions and the geometric and Stress Continuity conditions at interfaces. Moreover, the number of unknowns of this theory is independent of the layer numbers of the laminate. Based on the global–local higher-order theory, the discrete Kirchhoff element PDKT and refined triangular plate element PRT9 are presented for predicting interlaminar Stresses and displacements in laminated plates subjected to thermal loading. The two triangular elements satisfy the interelement C1 Continuity conditions. The numerical examples show that the in-plane Stresses and transverse shear Stresses can be accurately calculated by the direct constitutive equation approach. The equilibrium equation approach is employed to predict transverse normal Stresses.
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A new higher-order shear deformation theory based on global-local superposition and refined triangular plate element of composite laminate
Chinese Journal of Computational Mechanics, 2005Co-Authors: Wu ZhenAbstract:A new higher-order shear deformation theory based on global-local superposition technique is developed.The global displacement components are of the Reddy theory(1984) while local components are of the local displacement components of the Li X Y 1,2-3 double-superposition theory(1997).The present theory satisfies the free surface conditions and the geometric and Stress Continuity conditions at interfaces.At the same time,the theory compared with 1,2-3 theory greatly reduces the variables.A refined three-node triangular plate element(9 degrees of freedom in each node) based on new global-local higher-order theory is presented.Numerical results show that the refined triangular plate element is capable to accurately calculate global displacement and interlaminar Stress.
Dahsin Liu - One of the best experts on this subject based on the ideXlab platform.
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nonlinear analysis of composite plates using interlaminar shear Stress Continuity theory
Composites Engineering, 1993Co-Authors: Chunying Lee, Dahsin LiuAbstract:Abstract An interlaminar shear Stress Continuity theory (ISSCT) presented in a previous study can give excellent results for both the static and vibration analysis of composite beams. This theory is extended to study composite plates with geometric nonlinearity. The studies are based on nonlinear strain-displacement relations of the von Karman sense. The nonlinear bending and vibration of various composite plates are investigated. The postbuckling behavior of asymmetric plates is also examined. Both closed-form solutions and finite element results are obtained and compared with three-dimensional elasticity solutions. Some important results for composite plates with small aspect ratio and asymmetric lamination are presented. It is concluded that ISSCT is an accurate technique for studying laminated composite plates.
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static and vibration analysis of laminated composite beams with an interlaminar shear Stress Continuity theory
International Journal for Numerical Methods in Engineering, 1992Co-Authors: Chunying Lee, Dahsin LiuAbstract:A finite element method for Stress and vibration analysis of laminated composite beams was investigated. The analysis was based on a multilayered theory presented by Lu and Liu. This theory accounts for the Continuity of interlaminar shear Stress. The principle of minimum potential energy was used in the finite element formulation. The interlaminar shear Stress was obtained directly from the constitutive equations. It was verified that the present technique was able to give excellent results for displacements, Stresses and vibration frequencies for both thin and thick composite beams. The effects of the number of layers and the number of elements on the convergence were also discussed.
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an interlaminar Stress Continuity theory for laminated composite analysis
Computers & Structures, 1992Co-Authors: Chunying Lee, Dahsin LiuAbstract:Abstract A complete analysis of a new lamination theory presented in a previous investigation for studying the interlaminar Stresses in both thin and thick composite laminates is developed. This theory is based on a multiple-layer approach. Hermite cubic shape function is used as the interpolation function for composite layer assembly through the thickness direction. Because of the high-order shape function, the theory can satisfy the Continuity of both interlaminar shear Stress and interlaminar normal Stress exactly on the composite interface. It then is able to obtain the interlaminar Stresses directly from the constitutive equations. In addition, because of the high-order interpolation function, the transverse shear deformation is considered in the theory. Accordingly, the theory can be used for both thin and thick composite laminates. In this study, the composite laminates under cylindrical bending studied by Pagano are investigated to verify the new theory. Closed form solutions agree excellently with the elasticity results. A finite element technique based on the principle of minimum potential energy is also used for numerical analysis. The numerical results also show excellent agreement with the exact solution.
Sebastien Mistou - One of the best experts on this subject based on the ideXlab platform.
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mechanical behaviour of laminated composite beam by the new multi layered laminated composite structures model with transverse shear Stress Continuity
International Journal of Solids and Structures, 2003Co-Authors: Moussa Karama, K S Afaq, Sebastien MistouAbstract:Abstract This work presents a new multi-layer laminated composite structure model to predict the mechanical behaviour of multi-layered laminated composite structures. As a case study, the mechanical behaviour of laminated composite beam (90°/0°/0°/90°) is examined from both a static and dynamic point of view. The results are compared with the model “Sinus” and finite element method studied by Abou Harb. Results show that this new model is more precise than older ones as compared to the results by the finite element method (Abaqus). To introduce Continuity on the interfaces of each layer, the kinematics defined by Ossadzow was used. The equilibrium equations and natural boundary conditions are derived by the principle of virtual power. To validate the new proposed model, different cases in bending, buckling and free vibration have been considered.
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mechanical behaviour of laminated composite beam by the new multi layered laminated composite structures model with transverse shear Stress Continuity
International Journal of Solids and Structures, 2003Co-Authors: Moussa Karama, K S Afaq, Sebastien MistouAbstract:This work presents a new multi-layer laminated composite structure model to predict the mechanical behaviour of multi-layered laminated composite structures. As a case study, the mechanical behaviour of laminated composite beam (90� /0� /0� /90� ) is examined from both a static and dynamic point of view. The results are compared with the model ‘‘Sinus’’ and finite element method studied by Abou Harb. Results show that this new model is more precise than older ones as compared to the results by the finite element method (Abaqus). To introduce Continuity on the interfaces of each layer, the kinematics defined by Ossadzow was used. The equilibrium equations and natural boundary conditions are derived by the principle of virtual power. To validate the new proposed model, different cases in bending, buckling and free vibration have been considered. � 2002 Elsevier Science Ltd. All rights reserved.
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Analysis of Sandwich Composite Beams with a New Transverse Shear Stress Continuity Model
Journal of Sandwich Structures & Materials, 1999Co-Authors: Sebastien Mistou, Moussa Karama, B. Lorrain, J. P. FayeAbstract:This work presents a new composite beam model based on discrete layer theory. It enables the automatic verification of the Continuity of transverse shear Stresses by taking into account the Heaviside step function. The transverse shear is represented by a sine function which improves the accuracy of the results on the transverse shear Stress. The membrane refinement cosine function improves the warping of the straight section in bending deformations. In order to validate the proposed model, several problems in bending and free vibration are presented. For sandwich composite beams, the proposed new model satisfies exactly and automatically the Continuity conditions of displacements and Stresses at the interfaces, as well as the boundary conditions.
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bending buckling and free vibration of laminated composite with a transverse shear Stress Continuity model
Composites Part B-engineering, 1998Co-Authors: Moussa Karama, Abou B Harb, Sebastien Mistou, S CaperaaAbstract:Abstract This work presents a new laminated composite beam model based on discrete layer theory, the model is applied in statics and in dynamics on thin and thick beams. It allows one to satisfy automatically the Continuity of transverse shear Stresses by taking into account the Heaviside step function. The transverse shear is represented by a sine function (Touratier). This model introduces membrane refinement through a cosine function (Ossadzow, Muller and Touratier) contrary to the different models existing in the bibliography. The motion equations and the natural boundary conditions result from the virtual power principal. In order to validate the proposed model, several problems in bending, buckling and free vibration are presented.
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Bending, Buckling and Free Vibration of Sandwich Composite Beams with a Transverse Shear Stress Continuity Model
Mechanics of Sandwich Structures, 1998Co-Authors: Moussa Karama, Sebastien Mistou, B. Abou Harb, S CaperaaAbstract:This work presents a new composite beam model based on discrete layer theory. It allows to verify automatically the Continuity of transverse shear Stresses by taking into account the Heaviside step function. Besides, the transverse shear is represented by a sine function (Touratier, 1991). Moreover, this model introduces membrane refinement (Ossadzow and al., 1995).
