Department of Civil Engineering

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Author: search.filters.author.Singh, Shamsher BahadurSubject: search.filters.subject.Buckling

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Now showing 1 - 10 of 13
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    Mechanism for Predicting the Progressive Failure of Natural Fiber-Based Composites
    (Springer, 2022-07) Singh, Shamsher Bahadur
    The present study deals with the numerical investigation of buckling and postbuckling responses and failure of natural fiber-based composites and synthetic fiber-reinforced polymer composites under uni-axial compression. The unidirectional fibers are used for the composite aligned with the (0/90) directions. The plates are modelled using general purpose software Abaqus. All the edges of the plate are simply supported. By implementing the linear buckling analysis, the buckling load has been determined. Using the non-linear analysis and static Riks procedure, the composite's postbuckling behavior has also been predicted. The Tsai hill failure criterion is incorporated in the numerical analysis to predict the first-ply failure in the composite. In this study, three different composite models, i.e., Glass, Carbon and Flax fiber-reinforced composites are considered for the analysis. It is observed that the carbon fiber composite has the better buckling load capacity and the first ply failure load compared to glass and flax fiber-reinforced composites. It is further observed that the flax fiber-reinforced composite performs comparatively similar to the glass fiber reinforced composite. Based on the results, it is expected that the glass fiber reinforced composite can be replaced by the flax fiber-reinforced composites. In this study, the ultimate load has been considered when the plate is unable to take any further load in analysis. To precisely predict the ultimate failure of a composite, a methodology has been proposed to undertake the progressive failure analysis of composite by incorporating the UMAT subroutine in the Abaqus.
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    Performance of FRP Bridge Deck Under Flexural Loading
    (Springer, 2022-07) Singh, Shamsher Bahadur
    Fibre-reinforced polymers or FRPs are durable materials that are highly resistant to corrosive activity, have a high stiffness-to-weight ratio and are ideally suited for the construction of assembly lines into compact modules which can be easily installed. FRP production costs are therefore considerably higher than conventional concrete and steel materials. Hence overall cost savings is either due to decreased weight, faster building speed or lower maintenance and improved life span. In this study, the optimum cross-section of the stiffeners of the deck slab is determined from different shapes and sizes of stiffener, which offers high stiffness and strength. Along with, effect of different longitudinal and transverse modulus of stiffeners on the flexural capacity of deck is determined. It is observed that by keeping longitudinal modulus (E1) constant while varying the E1/E2 ratio, the trapezoidal shape stiffener provides the highest strength and stiffness. On the other hand, keeping E2 constant and varying the E1/G12 ratio trapezoidal stiffener shape shows the best result.
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    Postbuckling Response and Failure of Symmetric Laminated Plates with Rectangular Cutouts under Uni-axial Compression
    (Korea Institute of Science and Technology Information, 2008) Singh, Shamsher Bahadur
    This paper deals with the buckling and postbuckling responses and the progressive failure of square symmetric laminates with rectangular cutouts under uniaxial compression. A detailed investigation is made to show the effects of cutout size and cutout aspect ratio on prebuckling and postbuckling responses, failure loads and failure characteristics of (+45/−45/0/90)2s, (+45/−45)4s and (0/90)4s laminates. 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. In addition, the effects of boundary conditions on buckling load, failure loads, failure modes and maximum transverse deflection for a (+45/−45/0/90)2s laminate with and without cutout have also been presented. It is concluded that square laminates with small square cutouts have more postbuckling strength than without cutout, irrespective of boundary conditions.
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    Effects of boundary conditions on buckling and postbuckling responses of composite laminate with various shaped cutouts
    (Elsiever, 2010-02) Singh, Shamsher Bahadur
    The objective of the present work is to study the effects of flexural boundary conditions on buckling and post-buckling behavior of axially compressed quasi-isotropic laminate, (+45/−45/0/90)2s with various shaped cutouts (i.e., circular, square, diamond, elliptical–vertical and elliptical–horizontal) of various sizes using the finite element method. The FEM formulation is based on first order shear deformation theory and von Karman’s assumptions are used to incorporate geometric nonlinearity. 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 laminates clamped and simply supported on all edges have the highest and lowest buckling and postbuckling strength, respectively, irrespective of cutouts shape and size. It is also noted that a fully clamped laminate with large size elliptical–vertical cutout can take higher compressive buckling load than the laminate without cutout for same boundary condition.
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    Postbuckling response and failure of symmetric laminated plates with rectangular cutouts under in-plane shear
    (Techno Press, 2010-01-30) Singh, Shamsher Bahadur
    This paper deals with the buckling and postbuckling responses, and the progressive failure of square laminates of symmetric lay-up with a central rectangular cutout under in-plane shear load. A detailed investigation is made to show the effects of cutout size and cutout aspect ratio on the buckling and postbuckling responses, failure loads and failure characteristics of (+45/-45/0/90)2s, (+45/-45)4s and (0/90)4s laminates. 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. In addition, the effects of boundary conditions on buckling loads, failure loads, failure modes, and maximum transverse deflection for a (+45/-45/0/90)2s laminate with and without a square cutout have been presented. It is concluded that because of early onset of delamination at the net section of cutouts before first-ply failure, total strength of the laminate with very small cutouts can not be utilized.
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    Cutout shape and size effects on response of quasi-isotropic composite laminate under uni-axial compression
    (Techno Press, 2010-06) Singh, Shamsher Bahadur
    Cutouts are often provided in structural and aircraft components for ventilation, for access, inspection, electric lines and fuel lines or sometimes to lighten the structure. This paper addresses the effects of cutout shape (i.e., circular, square, diamond, elliptical-vertical and elliptical-horizontal) and size on buckling and postbuckling response of quasi-isotropic (i.e., (+45/−45/0/90)2s) composite laminate under uni-axial compression. The finite element method is used to carry out the investigation. The formulation is based on first order shear deformation theory and von Karman
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    Effect of Cutout Location on Postbuckiling Responses and Failure Characteristics of Composite Laminates
    (The Aeronautical Society of India, 2011) Singh, Shamsher Bahadur
    The objective of the present investigation is to study effects of locations of various shaped (i.e., circular, square and diamond) cutouts on stability and failure characteristics of simply-supported, axially-compressed quasi-isotropic laminate, (+45/-45/0/90)2s using finite element method. The FEM formulation is based on first order shear deformation theory wherein von Karman’s assumptions are used to incorporate geometric nonlinearity. 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 location of cutout has a significant effect on buckling and postbuckling strength of the laminate. It is also noted that the laminate with cutout centered at a distance greater than or equal to 0.75b (where, b is the width of the square laminate) from the loaded edge has negligible effect on buckling strength of the laminate.
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    Load interaction curves and postbuckling response of composite laminate with circular cutout under combined in-plane loading
    (Elsiever, 2011-07) Singh, Shamsher Bahadur
    The objective of this paper is to study the interaction curves along with buckling and postbuckling responses of a quasi-isotropic laminate with a centrally placed circular cutout of various sizes under uni-axial compression combined with in-plane shear loads (positive and negative). The present study is carried out using finite element method. The finite element formulation is based on the first order shear deformation theory and von Karman’s assumptions to incorporate geometric nonlinearity. The resulting nonlinear algebraic equations are solved by Newton–Raphson method. 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 pure compression- buckling, -first-ply failure and -ultimate failure strengths of the quasi-isotropic laminate with and without circular cutout decreases with increasing accompanying shear load. In addition, it is also noted that for a given uni-axial compression load, a quasi-isotropic laminate with and without a cutout can sustain higher negative shear load in comparison to the positive shear load.
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    Stability and failure of composite laminates with various shaped cutouts under combined in-plane loads
    (Elsiever, 2012-03) Singh, Shamsher Bahadur
    The objective of this paper is to study stability and failure of a composite laminate with a centrally placed cutout of various shapes (i.e., circular, square, diamond, elliptical-vertical and elliptical-horizontal) under combined action of uni-axial compression and in-plane shear loads. The FEM formulation based on the first order shear deformation theory and von Karman’s assumptions has been utilized. Newton–Raphson method is used to solve nonlinear algebraic equations. Failure of a lamina is predicted by the 3-D Tsai–Hill criterion whereas the onset of delamination is predicted by the interlaminar failure criterion. The effects of cutout shape, direction of shear load and composite lay-up on buckling and postbuckling responses, failure loads and failure characteristics of the laminate has been discussed. An efficient utilization of material strength is observed in the case of laminate with circular cutout as compared to the laminate with other shaped cutouts. In addition, it is also concluded that although the buckling strength of the (0/90)4s laminate is lower than that of the (+45/−45/0/90)2s and (45/−45)4s laminates, but its strength is increased in the advanced stage of postbuckling deformation.
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    Effects of flexural boundary conditions on failure and stability of composite laminate with cutouts under combined in-plane loads
    (Elsiever, 2013-02) Singh, Shamsher Bahadur
    In the present study, an investigation on the effects of flexural boundary conditions on prebuckling and postbuckling responses, failure loads and characteristics of a quasi-isotropic [i.e., (+45/−45/0/90)2s] square laminate with and without a central cutout of various shapes is carried out under combined in-plane loads [i.e., uni-axial compression combined with in-plane shear (positive and negative)] using finite element method. The finite element formulation is based on the first order shear deformation theory in conjunction with the von Karman’s assumptions to incorporate geometric nonlinearity. 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 under combined loading conditions, buckling and postbuckling strengths and failure loads of the laminate are reduced by the introduction of a cutout at the center of the laminate, irrespective of boundary conditions. It is also noted that the laminate with and without cutout has maximum buckling, first-ply failure and postbuckling strengths (at a particular value of transverse deflection) for BC3 (i.e., clamped on all edges) boundary conditions whereas these values are minimum for BC1 (i.e., simply-supported on all edges) boundary conditions, for both directions of shear load