The Experts below are selected from a list of 42039 Experts worldwide ranked by ideXlab platform
F.x. Irisarri - One of the best experts on this subject based on the ideXlab platform.
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Determination of the longitudinal compressive strength of a CFRP ply through a tensile test on a laminate
Composites Part A: Applied Science and Manufacturing, 2018Co-Authors: Frédéric Laurin, P. Paulmier, F.x. IrisarriAbstract:In this study, an innovative test is proposed to identify the longitudinal compressive strength of a unidirectional ply. The key idea consists in designing a laminate that, when subjected to a tensile loading, fails by compressive failure in its central 90°-ply, due to the Poisson Effect, without any prior damage. Six specimens have been tensile tested to failure. No intra-laminar matrix damage could be detected before the final failure. Fibre kinking in the 90°-ply is observed experimentally in the failed specimens. This damage mechanism, located in the gauge section of the specimens, leads to the final failure. A fast computational identification method is used to determine the longitudinal compressive stress and strain within the 90-ply at failure, from this specific tensile test. The identified average failure properties are consistent with those obtained through conventional compression tests, but the associated scattering is much lower. Consequently, this innovative method leads to an increase in the design allowable, resulting in higher performance designs.
Omer Civalek - One of the best experts on this subject based on the ideXlab platform.
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a size dependent shear deformation beam model based on the strain gradient elasticity theory
International Journal of Engineering Science, 2013Co-Authors: Bekir Akgoz, Omer CivalekAbstract:Abstract A new size-dependent higher-order shear deformation beam model is developed based on modified strain gradient theory. The model captures both the microstructural and shear deformation Effects without the need for any shear correction factors. The governing equations and boundary conditions are derived by using Hamilton’s principle. The static bending and free vibration behavior of simply supported microbeams are investigated. Analytical solutions including Poisson Effect for deflections under point and uniform loads and for first three natural frequencies are obtained by Navier solution. The results are compared with other beam theories and other classical and non-classical models. A detailed parametric study is carried out to show the influences of thickness-to-material length scale parameter ratio, slenderness ratio and shear deformation on deflections and natural frequencies of microbeams. It is observed that Effect of shear deformation becomes more significant for both smaller slenderness ratios and higher modes.
J N Reddy - One of the best experts on this subject based on the ideXlab platform.
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A NONLOCAL CURVED BEAM MODEL BASED ON A MODIFIED COUPLE STRESS THEORY
International Journal of Structural Stability and Dynamics, 2011Co-Authors: Yiping Liu, J N ReddyAbstract:A nonlocal Timoshenko curved beam model is developed using a modified couple stress theory and Hamilton's principle. The model contains a material length scale parameter that can capture the size Effect, unlike the classical Timoshenko beam theory. Both bending and axial deformations are considered, and the Poisson Effect is incorporated in the model. The newly developed nonlocal model recovers the classical model when the material length scale parameter and Poisson's ratio are both taken to be zero and the straight beam model when the radius of curvature is set to infinity. In addition, the nonlocal Bernoulli–Euler curved beam model can be realized when the normal cross-section assumption is restated. To illustrate the new model, the static bending and free vibration problems of a simply supported curved beam are solved by directly applying the formulas derived. The numerical results for the static bending problem reveal that both the deflection and rotation of the simply supported beam predicted by the new model are smaller than those predicted by the classical Timoshenko curved beam model. Also, the differences in both the deflection and rotation predicted by the current and classical Timoshenko model are very large when the beam thickness is small, but they diminish with the increase of the beam height. Similar trends are observed for the free vibration problem, where it is shown that the natural frequency predicted by the nonlocal model is higher than that by the classical model, and the difference between them is significantly large only for very thin beams. These predicted trends of the size Effect at the micron scale agree with those observed experimentally.
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a microstructure dependent timoshenko beam model based on a modified couple stress theory
Journal of The Mechanics and Physics of Solids, 2008Co-Authors: H M, X L Gao, J N ReddyAbstract:Abstract A microstructure-dependent Timoshenko beam model is developed using a variational formulation. It is based on a modified couple stress theory and Hamilton's principle. The new model contains a material length scale parameter and can capture the size Effect, unlike the classical Timoshenko beam theory. Moreover, both bending and axial deformations are considered, and the Poisson Effect is incorporated in the current model, which differ from existing Timoshenko beam models. The newly developed non-classical beam model recovers the classical Timoshenko beam model when the material length scale parameter and Poisson's ratio are both set to be zero. In addition, the current Timoshenko beam model reduces to a microstructure-dependent Bernoulli–Euler beam model when the normality assumption is reinstated, which also incorporates the Poisson Effect and can be further reduced to the classical Bernoulli–Euler beam model. To illustrate the new Timoshenko beam model, the static bending and free vibration problems of a simply supported beam are solved by directly applying the formulas derived. The numerical results for the static bending problem reveal that both the deflection and rotation of the simply supported beam predicted by the new model are smaller than those predicted by the classical Timoshenko beam model. Also, the differences in both the deflection and rotation predicted by the two models are very large when the beam thickness is small, but they are diminishing with the increase of the beam thickness. Similar trends are observed for the free vibration problem, where it is shown that the natural frequency predicted by the new model is higher than that by the classical model, with the difference between them being significantly large only for very thin beams. These predicted trends of the size Effect in beam bending at the micron scale agree with those observed experimentally. Finally, the Poisson Effect on the beam deflection, rotation and natural frequency is found to be significant, which is especially true when the classical Timoshenko beam model is used. This indicates that the assumption of Poisson's Effect being negligible, which is commonly used in existing beam theories, is inadequate and should be individually verified or simply abandoned in order to obtain more accurate and reliable results.
Frédéric Laurin - One of the best experts on this subject based on the ideXlab platform.
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Determination of the longitudinal compressive strength of a CFRP ply through a tensile test on a laminate
Composites Part A: Applied Science and Manufacturing, 2018Co-Authors: Frédéric Laurin, P. Paulmier, F.x. IrisarriAbstract:In this study, an innovative test is proposed to identify the longitudinal compressive strength of a unidirectional ply. The key idea consists in designing a laminate that, when subjected to a tensile loading, fails by compressive failure in its central 90°-ply, due to the Poisson Effect, without any prior damage. Six specimens have been tensile tested to failure. No intra-laminar matrix damage could be detected before the final failure. Fibre kinking in the 90°-ply is observed experimentally in the failed specimens. This damage mechanism, located in the gauge section of the specimens, leads to the final failure. A fast computational identification method is used to determine the longitudinal compressive stress and strain within the 90-ply at failure, from this specific tensile test. The identified average failure properties are consistent with those obtained through conventional compression tests, but the associated scattering is much lower. Consequently, this innovative method leads to an increase in the design allowable, resulting in higher performance designs.
Alireza Daneshmehr - One of the best experts on this subject based on the ideXlab platform.
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size dependent buckling analysis of microbeams based on modified couple stress theory with high order theories and general boundary conditions
International Journal of Engineering Science, 2014Co-Authors: Mostafa Mohammadabadi, Alireza DaneshmehrAbstract:Abstract In this research, buckling analysis of three microbeam models are investigated based on modified couple stress theory. Using Euler–Bernoulli beam theory (EBT), Timoshenko beam theory (TBT) and Reddy beam theory (RBT), the Effect of shear deformation is presented. To examine the Effect of boundary condition, three kinds of boundary conditions i.e. hinged–hinged, clamped–hinged and clamped–clamped boundary conditions, are considered. These nonclassical microbeam models incorporated with Poisson Effect, contain a material length scale parameter and can capture the size Effect. These models can degenerate into the Classical models if the material length scale parameter and Poisson’s ratio are both taken to be zero. Governing equations and boundary conditions are derived by using principle of minimum potential energy. Generalized differential quadrature (GDQ) method is employed to solve the governing differential equations. Also an analytical solution is applied to determine the critical buckling load of microbeams with hinged–hinged boundary condition. Comparison between the results of GDQ and analytical methods reveals the accuracy of GDQ method. Some numerical results are exhibited to indicate the influences of beam thickness, material length scale parameter and Poisson’s ratio on the critical buckling load of these microbeams.