Department of Civil Engineering

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

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Now showing 1 - 6 of 6
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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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    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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    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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    Effects of Boundary Conditions on Postbuckling Strengths of Composite Laminate with Various Shaped Cutouts under In-Plane Shear
    (Scientific Research Publishing I, 2013-04) Singh, Shamsher Bahadur
    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 responses, 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-isotropic 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 is maximum, while it is minimum for (45/—45)4s laminate with circular cutout, irrespective of boundary conditions.
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