The Experts below are selected from a list of 198 Experts worldwide ranked by ideXlab platform
J Loughlan - One of the best experts on this subject based on the ideXlab platform.
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the Buckling of cfrp composite plates in compression and shear and thin walled composite tubes in torsion the effects of bend twist coupling and the applied shear direction on Buckling performance
Thin-walled Structures, 2019Co-Authors: J LoughlanAbstract:Abstract The influence of flexural anisotropy or bend-twist coupling on the Buckling performance of CFRP composite plates in compression and shear and thin-walled CFRP composite tubes in torsion is examined in this paper using the finite strip method of analysis. The finite strip formulation employed in the analysis procedure is readily able to deal with the many complexities associated with typical laminated composite construction. Lay-up configurations resulting in membrane anisotropy, flexural anisotropy and membrane-flexural coupling are all easily dealt with. The strip perturbation or Buckling Displacement fields are postulated to vary sinusoidally along the strip length and algebraicly across the strip width and any combination of linearly varying bi-axial tension or compression coupled with in-plane shear loading on the strip can be accommodated. The paper gives an in-depth understanding of the complex Buckling mechanics associated with flexural anisotropy in polymer composite construction and highlights the importance of realising the significance of the applied in-plane shear or torque direction on Buckling performance. Markedly different stability levels are shown to be in existence for the load cases of positive and negative shear in composite plates and for the clockwise and anticlockwise torsional loading of thin-walled composite tubes. This situation is, of course, not realised in isotropic metal construction or in orthotropic composite construction since such material systems are devoid of the effects of bend-twist coupling.
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The Buckling of CFRP composite plates in compression and shear and thin-walled composite tubes in torsion – The effects of bend-twist coupling and the applied shear direction on Buckling performance
Thin-Walled Structures, 2019Co-Authors: J LoughlanAbstract:Abstract The influence of flexural anisotropy or bend-twist coupling on the Buckling performance of CFRP composite plates in compression and shear and thin-walled CFRP composite tubes in torsion is examined in this paper using the finite strip method of analysis. The finite strip formulation employed in the analysis procedure is readily able to deal with the many complexities associated with typical laminated composite construction. Lay-up configurations resulting in membrane anisotropy, flexural anisotropy and membrane-flexural coupling are all easily dealt with. The strip perturbation or Buckling Displacement fields are postulated to vary sinusoidally along the strip length and algebraicly across the strip width and any combination of linearly varying bi-axial tension or compression coupled with in-plane shear loading on the strip can be accommodated. The paper gives an in-depth understanding of the complex Buckling mechanics associated with flexural anisotropy in polymer composite construction and highlights the importance of realising the significance of the applied in-plane shear or torque direction on Buckling performance. Markedly different stability levels are shown to be in existence for the load cases of positive and negative shear in composite plates and for the clockwise and anticlockwise torsional loading of thin-walled composite tubes. This situation is, of course, not realised in isotropic metal construction or in orthotropic composite construction since such material systems are devoid of the effects of bend-twist coupling.
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The influence of mechanical couplings on the compressive stability of anti-symmetric angle-ply laminates
Composite Structures, 2002Co-Authors: J LoughlanAbstract:Abstract The compressive stability of anti-symmetric angle-ply laminated plates with particular reference to the degrading influence of membrane–flexural coupling is reported in this paper. The degree of membrane–flexural coupling in the laminated composite plates is varied, essentially, by altering the ply-angle and the number of plies in the laminated stack for a given composite material system. The coupled compressive Buckling solutions are determined in the paper using the finite strip method of analysis and the Buckling Displacement fields of the strip formulation are those which are able to provide zero in-plane normal movement at the edge boundaries of the laminated plates. Results are given for anti-symmetric angle-ply laminated plates subjected to uniaxial compression and these have been obtained from fully converged finite strip structural models. Validation of the finite strip formulation is indicated in the paper through comparisons with exact solutions where appropriate. Increasing the number of plies in the laminated system is seen to reduce the degree of coupling and the critical stress levels are noted to tend towards the plate orthotropic solutions. The ply-angle corresponding to the optimised Buckling stress for any particular laminate is noted in the paper to be influenced by the support boundary conditions at the plates unloaded edges. For any particular laminate the minimum critical Buckling stress and corresponding natural half-wavelength of the Buckling mode are shown to be highly sensitive to ply-angle variation. Some post-Buckling results are presented in the paper and these have been determined using the finite element method of analysis. The influence of membrane–flexural coupling is shown to be significant throughout the compressive post-Buckling history of the laminated plates. The optimised ply-angle with regard to the critical compressive Buckling stress of square simply supported anti-symmetric angle-ply laminates is shown to be less effective in the post-Buckling range with regard to post-buckled compressional stiffness.
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The compressive Buckling performance of anti-symmetric composite laminates and the effect on behaviour of membrane-flexural coupling
Aeronautical Journal, 2002Co-Authors: J LoughlanAbstract:The compressive stability of anti-symmetric angle-ply laminated plates with particular reference to the degrading influence of membrane-flexural coupling is reported in this paper. A specific configuration of anti-symmetric laminate is dealt with in the paper and this takes the form [θ/-θ] n whereby 2n is the total number of plies in the laminated stack. With regard to compressive Buckling the paper gives an indication that anti-symmetric laminates with 8 plies or more will yield performance levels which are almost identical to their symmetric counterparts. The degree of membrane-flexural coupling in the laminated composite plates is varied, essentially, by changing the ply angle and also by altering the number of plies in the laminated stack, for a given composite material system. The coupled compressive Buckling solutions are determined using the finite strip method of analysis. In order to provide an adequate level of flexibility in the analysis procedure and to ensure a high level of accuracy of solution, the Buckling Displacement fields of the strip formulation are those which are described in a multi-term form. Results are given for anti-symmetric angle-ply laminated plates subjected to uniaxial and biaxial compression and these have been obtained from fully converged finite strip structural models. Validation of the finite strip formulation is indicated in the paper through comparisons with exact solutions where appropriate. The natural half-wavelength of the compressive Buckling mode of the composite plates is shown to be significantly influenced by variation in the ply angle. Increasing the number of plies in the laminated system is seen to reduce the degree of coupling and the critical stress levels are noted to tend towards the plate orthotropic solutions. The ply angle corresponding to the optimised compressive Buckling stress for any particular laminate is noted in the paper to be influenced by the support boundary conditions at the plates unloaded edges.
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The influence of bend–twist coupling on the shear Buckling response of thin laminated composite plates
Thin-Walled Structures, 1999Co-Authors: J LoughlanAbstract:Abstract The finite strip method of analysis has been used in this paper to examine the effect of bend–twist coupling on the shear Buckling behaviour of laminated composite constructions. The distorted nodal lines of the shear Buckling mode and its complex deformation state in general are readily accounted for in the analysis procedure through the multi-term nature of the finite strip Buckling Displacement field and the appropriate level of structural modelling. The degree of bend–twist coupling in the laminated composite plates is varied by changing the level of anisotropy in the plies and by altering the lay-up configuration of the plies in the laminated stack. Symmetric laminates of a balanced and unbalanced nature are given consideration. It is shown that, for a given degree of anisotropy in the plies of a laminate and for a given laminate thickness, the stacking sequence of the plies significantly alters the degree of bend–twist coupling. The shear Buckling performance of composite plates having the same dimensions and being made from the same material are therefore shown in the paper to be quite different. The preclusion of the bend–twist coupling coefficients in the solution procedure of the finite strip method allows the shear Buckling orthotropic solution to be determined. Comparisons between the coupled and orthotropic solutions are shown in the paper to be markedly different.
M. Ramji - One of the best experts on this subject based on the ideXlab platform.
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Experimental and numerical studies on the Buckling and post-Buckling behavior of single blade-stiffened CFRP panels
Composite Structures, 2018Co-Authors: Naresh Reddy Kolanu, Gangadharan Raju, M. RamjiAbstract:Abstract The aim of this study is to experimentally investigate the stability behavior and failure characteristics of carbon fibre reinforced polymer (CFRP) composite panels with secondary bonded blade stiffener under compression. Various experimental techniques like 3D-digital image correlation (DIC), acoustic emission (AE), strain gaging and infrared thermography were employed together for capturing the Buckling, post-Buckling response and failure characteristics of test panels. The 3D-DIC technique was employed for determining the Buckling and post-Buckling Displacement fields of the test panel. The strain gage data was used for accurate prediction of the onset of Buckling phenomenon of the test panels. Parametric data obtained from the AE technique was analysed for identifying and classifying the various damage events encountered in the test panel. In addition, finite element simulation of the CFRP stiffened panel under compression was performed to validate the experimental post-Buckling results. In this work, Hashin’s failure criteria was used to study the initiation of various failure modes in the critical regions of the stiffened panel. The proposed unified experimental approach can provide more insights on the post-Buckling behavior and failure characteristics of single blade stiffened CFRP panels, thereby helping engineers in designing damage tolerant composite structures.
Cm Cees Menken - One of the best experts on this subject based on the ideXlab platform.
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Mode-Reduction Applied to Initial Post-Buckling Behavior
DIANA Computational Mechanics ‘84, 1994Co-Authors: G-jma Gerd-jan Schreppers, Cm Cees MenkenAbstract:This paper presents a perturbation approach for analyzing the (initial) post-Buckling behavior of elastic structures. In this perturbation a small number of Buckling modes is taken into account. This approach results in a potential energy function which is defined in terms of amplitudes of the selected modes. The post-Buckling Displacement field is solved from the reduced set of equilibrium equations where the unknowns are the amplitudes of the Euler modes which are selected for the asymptotic expansion. To perform this technique the segment PERTUR in module *EULER is designed in DIANA 6.0. The theory of this segment and two calculating examples are demonstrated.
Philippe Sautet - One of the best experts on this subject based on the ideXlab platform.
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Highly strained structure of a four-layer deposit of Pd on Ni(110): a coupled theoretical and experimental study.
Physical review letters, 2002Co-Authors: Jean-sébastien Filhol, M.c. Saint-lager, M. De Santis, P. Dolle, D. Simon, R. Baudoing-savois, Jean-claude Bertolini, Philippe SautetAbstract:The structure of a four monolayer deposit of Pd on Ni(110) has been determined by a combination of x-ray diffraction experiments and density-functional theory calculations. This Pd film presents, after annealing at 500 K, a (Nx2) reconstruction associated with a large enhancement of its catalytic activity. The N superstructure, along the dense [11;0] direction, comes from periodic edge dislocations initiated by a vacancy in the first Pd layer. In the perpendicular direction, the doubling of the period originates in a pairing-Buckling Displacement of the rows. This study evidences a new Pd atoms arrangement with quasi-four-fold hollow sites on the surface, which could play an important role in the exceptional catalytic activity.
G. Gendron - One of the best experts on this subject based on the ideXlab platform.
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Optimal design of geodesically stiffened composite cylindrical shells
Composites Engineering, 1993Co-Authors: Zafer Gürdal, G. GendronAbstract:Abstract An optimization system based on the general-purpose finite element code CSM Testbed (recently renamed COMET) and the optimizaion program ADS was used to obtain minimum-weight geodesically stiffened composite cylindrical shells that are representative of segments of a generic wide-body aircraft fuselage structure. Ply thicknesses and orientations of the skin laminate, and stiffener heights were used as design variables, and Buckling, Displacement and material failure constraints were imposed on the design. A preliminary design study of geodesically stiffened shells loaded by axial compression, torsion and combined compression-torsion was conducted. For comparison purposes, optimal designs of unstiffened shells, and ring- and longitudinal stringer-stiffened shells were also studied. Trends in the design of geodesically stiffened shells were identified.
