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S B Singh - One of the best experts on this subject based on the ideXlab platform.
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Effects of Boundary Conditions on Postbuckling Strengths of Composite Laminate with Various Shaped Cutouts
2016Co-Authors: Under In-plane Shear, Dinesh Kumar, S B SinghAbstract:Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Cutouts are often provided in composite structural components for practical reasons. For instance, aircraft components such as wingspar, fuselage and ribs are provided with cutouts for access, inspection, fuel lines and electric lines or to reduce the overall weight. This paper addresses the effect of boundary condition on buckling and postbuckling re-sponses, failure loads, and failure characteristics of composite laminate with various shaped cutouts (i.e., circular, square, diamond, elliptical-vertical and elliptical-horizontal) and having different lay-ups under in-plane shear (positive and negative) load, using finite-element method. The FEM formulation is based on the first order shear deformation theory in conjunction with geometric nonlinearity using von Karman’s assumptions. The 3-D Tsai-Hill Criterion is used to predict the failure of a lamina while the onset of delamination is predicted by the interlaminar failure Criterion. It is observed that the effect of boundary condition on buckling, first-ply failure and ultimate failure loads of a quasi-iso-tropic laminate with cutout is more for positive shear load than that for the negative shear load for almost all cutout shapes. It is also noted that under in-plane shear loads postbuckling stiffness of (0/90)4s laminate with circular cutout i
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postbuckling strengths of composite laminate with various shaped cutouts under in plane shear
Composite Structures, 2010Co-Authors: Dinesh Kumar, S B SinghAbstract:Abstract The aim of present investigation is to study the buckling and postbuckling response and strengths under positive and negative in-plane shear loads of simply-supported composite laminate with various shaped cutouts (i.e., circular, square, diamond, elliptical-vertical and elliptical-horizontal) of various sizes using finite-element method. The FEM formulation is based on the first order shear deformation theory which incorporates geometric nonlinearity using von Karman’s assumptions. The 3-D Tsai-Hill Criterion is used to predict the failure of a lamina while the onset of delamination is predicted by the interlaminar failure Criterion. The effect of cutout shape, size and direction of shear load on buckling and postbuckling responses, failure loads and failure characteristics of quasi-isotropic [i.e., (+45/−45/0/90) 2s ] laminate has been discussed. In addition, the effect of composite lay-up [i.e., (+45/−45/0/90) 2s, (45/−45) 4s and (0/90) 4s ] has also been reported. It is observed that the cutout shape has considerable effect on the buckling and postbucking behaviour of the quasi-isotropic laminate with large size cutout. It is also observed that the direction of shear load and composite lay-up have substantial influence on strength and failure characteristics of the laminate.
Ali Fatemi - One of the best experts on this subject based on the ideXlab platform.
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effects of fiber orientation and anisotropy on tensile strength and elastic modulus of short fiber reinforced polymer composites
Composites Part B-engineering, 2015Co-Authors: Seyyedvahid Mortazavian, Ali FatemiAbstract:Abstract An experimental study was conducted to investigate anisotropy effects on tensile properties of two short glass fiber reinforced thermoplastics. Tensile tests were performed in various mold flow directions and with two thicknesses. A shell–core morphology resulting from orientation distribution of fibers influenced the degree of anisotropy. Tensile strength and elastic modulus nonlinearly decreased with specimen angle and Tsai–Hill Criterion was found to correlate variation of these properties with the fiber orientation. Variation of tensile toughness with fiber orientation and strain rate was evaluated and mechanisms of failure were identified based on fracture surface microscopic analysis and crack propagation paths. Fiber length, diameter, and orientation distribution mathematical models were also used along with analytical approaches to predict tensile strength and elastic modulus form tensile properties of constituent materials. Laminate analogy and modified Tsai–Hill criteria provided satisfactory predictions of elastic modulus and tensile strength, respectively.
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fatigue behavior and predictive modeling of short fiber thermoplastic composites
Procedia Engineering, 2015Co-Authors: Ali Fatemi, Seyyedvahid Mortazavian, Abolhasan KhosrovanehAbstract:Abstract Cyclic deformation and fatigue behavior of two short fiber thermoplastic composites (SFTCs) under a number of loading and environmental conditions are investigates. The considered environmental effects include those of low and elevated temperatures as well as moisture (or water absorption). Fatigue behavior is also explored under the action of non-zero mean stress (or R ratio) in addition to fully-reversed ( R = -1), as well as various cyclic loading frequencies. Material anisotropy and geometrical discontinuity effects (i.e. stress concentration) are other aspects considered in this study. Based on experimental observations and analysis, a number of analytical and empirical models are developed for predicting fatigue behavior under different conditions. Empirical equations are presented to characterize self-heating under cyclic loading. Tsai-Hill Criterion is applied to account for the effect of fiber orientation on fatigue life. Mean stress effect is corrected with several mean stress parameters and a shift factor of Arrhenius type is defined to characterize the effect of temperature on fatigue life. Two methodologies are presented to estimate fatigue properties based on tensile properties. Estimation of notched fatigue behavior based on smooth fatigue behavior is also presented.
Dinesh Kumar - One of the best experts on this subject based on the ideXlab platform.
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Effects of Boundary Conditions on Postbuckling Strengths of Composite Laminate with Various Shaped Cutouts
2016Co-Authors: Under In-plane Shear, Dinesh Kumar, S B SinghAbstract:Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Cutouts are often provided in composite structural components for practical reasons. For instance, aircraft components such as wingspar, fuselage and ribs are provided with cutouts for access, inspection, fuel lines and electric lines or to reduce the overall weight. This paper addresses the effect of boundary condition on buckling and postbuckling re-sponses, failure loads, and failure characteristics of composite laminate with various shaped cutouts (i.e., circular, square, diamond, elliptical-vertical and elliptical-horizontal) and having different lay-ups under in-plane shear (positive and negative) load, using finite-element method. The FEM formulation is based on the first order shear deformation theory in conjunction with geometric nonlinearity using von Karman’s assumptions. The 3-D Tsai-Hill Criterion is used to predict the failure of a lamina while the onset of delamination is predicted by the interlaminar failure Criterion. It is observed that the effect of boundary condition on buckling, first-ply failure and ultimate failure loads of a quasi-iso-tropic laminate with cutout is more for positive shear load than that for the negative shear load for almost all cutout shapes. It is also noted that under in-plane shear loads postbuckling stiffness of (0/90)4s laminate with circular cutout i
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postbuckling strengths of composite laminate with various shaped cutouts under in plane shear
Composite Structures, 2010Co-Authors: Dinesh Kumar, S B SinghAbstract:Abstract The aim of present investigation is to study the buckling and postbuckling response and strengths under positive and negative in-plane shear loads of simply-supported composite laminate with various shaped cutouts (i.e., circular, square, diamond, elliptical-vertical and elliptical-horizontal) of various sizes using finite-element method. The FEM formulation is based on the first order shear deformation theory which incorporates geometric nonlinearity using von Karman’s assumptions. The 3-D Tsai-Hill Criterion is used to predict the failure of a lamina while the onset of delamination is predicted by the interlaminar failure Criterion. The effect of cutout shape, size and direction of shear load on buckling and postbuckling responses, failure loads and failure characteristics of quasi-isotropic [i.e., (+45/−45/0/90) 2s ] laminate has been discussed. In addition, the effect of composite lay-up [i.e., (+45/−45/0/90) 2s, (45/−45) 4s and (0/90) 4s ] has also been reported. It is observed that the cutout shape has considerable effect on the buckling and postbucking behaviour of the quasi-isotropic laminate with large size cutout. It is also observed that the direction of shear load and composite lay-up have substantial influence on strength and failure characteristics of the laminate.
Seyyedvahid Mortazavian - One of the best experts on this subject based on the ideXlab platform.
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effects of fiber orientation and anisotropy on tensile strength and elastic modulus of short fiber reinforced polymer composites
Composites Part B-engineering, 2015Co-Authors: Seyyedvahid Mortazavian, Ali FatemiAbstract:Abstract An experimental study was conducted to investigate anisotropy effects on tensile properties of two short glass fiber reinforced thermoplastics. Tensile tests were performed in various mold flow directions and with two thicknesses. A shell–core morphology resulting from orientation distribution of fibers influenced the degree of anisotropy. Tensile strength and elastic modulus nonlinearly decreased with specimen angle and Tsai–Hill Criterion was found to correlate variation of these properties with the fiber orientation. Variation of tensile toughness with fiber orientation and strain rate was evaluated and mechanisms of failure were identified based on fracture surface microscopic analysis and crack propagation paths. Fiber length, diameter, and orientation distribution mathematical models were also used along with analytical approaches to predict tensile strength and elastic modulus form tensile properties of constituent materials. Laminate analogy and modified Tsai–Hill criteria provided satisfactory predictions of elastic modulus and tensile strength, respectively.
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fatigue behavior and predictive modeling of short fiber thermoplastic composites
Procedia Engineering, 2015Co-Authors: Ali Fatemi, Seyyedvahid Mortazavian, Abolhasan KhosrovanehAbstract:Abstract Cyclic deformation and fatigue behavior of two short fiber thermoplastic composites (SFTCs) under a number of loading and environmental conditions are investigates. The considered environmental effects include those of low and elevated temperatures as well as moisture (or water absorption). Fatigue behavior is also explored under the action of non-zero mean stress (or R ratio) in addition to fully-reversed ( R = -1), as well as various cyclic loading frequencies. Material anisotropy and geometrical discontinuity effects (i.e. stress concentration) are other aspects considered in this study. Based on experimental observations and analysis, a number of analytical and empirical models are developed for predicting fatigue behavior under different conditions. Empirical equations are presented to characterize self-heating under cyclic loading. Tsai-Hill Criterion is applied to account for the effect of fiber orientation on fatigue life. Mean stress effect is corrected with several mean stress parameters and a shift factor of Arrhenius type is defined to characterize the effect of temperature on fatigue life. Two methodologies are presented to estimate fatigue properties based on tensile properties. Estimation of notched fatigue behavior based on smooth fatigue behavior is also presented.
Marino Quaresimin - One of the best experts on this subject based on the ideXlab platform.
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influence of temperature and thickness on the off axis behaviour of short glass fibre reinforced polyamide 6 6 cyclic loading
Composites Part A-applied Science and Manufacturing, 2010Co-Authors: M De Monte, E Moosbrugger, Marino QuaresiminAbstract:Abstract This paper investigates the anisotropic properties of short glass fibre reinforced polyamide 6.6 (PA66-GF35) under tension–tension and tension–compression cyclic loading. Tensile fatigue tests were carried out on dog-bone specimens, machined out from injection-moulded plates 80 × 80 mm, of three different thicknesses t (1 and 3 mm) at three different nominal fibre orientation angles θ (0°, 30° and 90°). The tests were carried out at RT as well as at 130 °C. The Tsai–Hill failure Criterion, modified to account for cyclic loading, is applied to the fatigue data for estimating the fatigue strength parameters of the material under investigation. Results are compared to the strength parameters obtained under quasi-static loading in a previous part of this work [De Monte M, Moosbrugger E, Quaresimin M. Influence of temperature and thickness on the off-axis behaviour of short glass fibre reinforced polyamide 6.6 – quasi-static loading. Composites: Part A, 2010;41(10):1368–79]. The experimental results highlight how specimen thickness remarkably affects mechanical properties: the thinner the specimen the higher will be the degree of anisotropy. Also temperature strongly reduces the fatigue strength under cyclic loading. The Tsai–Hill Criterion allows for an adequate fitting of experimental data at the investigated temperatures and load ratios.
