Department of Civil Engineering

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Author: search.filters.author.Watts, Gaurav

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    Tunable thermal postbuckling response of imperfect skew sandwich plates with auxetic core and FGCNTRC facings using isogeometric approach
    (Elsevier, 2024-04) Watts, Gaurav; Kumar, Rajesh; Patel, Shuvendu Narayan
    The present work investigates the stability characteristics of skew sandwich plates with functionally graded (FG) facings reinforced with carbon nanotubes having temperature-dependent properties and a re-entrant auxetic core with tunable material properties using isogeometric analysis. The continuous function for material properties of the CNTs is obtained by interpolating the parameters at different temperature values using the fourth-degree polynomial, and resultant properties for the facings are determined using the modified rule of mixtures with the efficiency parameters. The mechanical and thermal properties of the reentrant auxetic core are based on modified Gibson’s relations. The equations of equilibrium are derived using the principle of virtual displacements, which are discretised through the approximation of solution and geometrical variables using B-spline basis functions. Several parametric studies are conducted to study the influence of type and magnitude of initial geometric imperfection, CNT distribution pattern in facings, cell angle of the auxetic core, rib length to thickness ratio, skew angle and boundary conditions on linear and nonlinear thermal post-buckling characteristics of the sandwich plate. New findings on the influence of geometric imperfection and auxetic core parameters on the thermal postbuckling behaviour of sandwich plates are presented for the first time, which may contribute towards a better understanding of the stability behaviour of lightweight structures.
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    Nonlinear vibration and instability of a randomly distributed CNT-reinforced composite plate subjected to localized in-plane parametric excitation
    (Elsevier, 2022-01) Kumar, Rajesh; Patel, Shuvendu Narayan; Watts, Gaurav
    This study presents a semi-analytical formulation for the nonlinear vibration and dynamic instability of a randomly distributed carbon nanotube-reinforced composite (RD-CNTRC) plate. Three cases of localized in-plane periodic loadings are studied. The analytical stress fields within the RD-CNTRC plate for all the in-plane stress components (σij, (i, j = x, y)) are developed by solving the in-plane elastic problem using Airy's stress approach. The effective mechanical properties of the RD-CNTRC plate are evaluated by the Eshelby-Mori-Tanaka technique. The plate is modeled based on higher-order shear deformation theory (HSDT) in conjunction with the von-Kármán nonlinearity. Using Hamilton's principle, the governing partial differential equations (PDEs) are derived, whose approximate solution is sought, referring to the Galerkin method. The resulting nonlinear ODEs are solved using the Incremental Harmonic Balance (IHB) Method to compute the nonlinear vibration response of the RD-CNTRC plate. Further dropping the nonlinear terms, these ODEs are solved by Bolotin's method to trace the instability region. The proposed semi-analytical method is an effective strategy for studying the influence of different parameters such as agglomeration models, CNT mass fraction, pre-loading, and boundary conditions on the nonlinear vibration and dynamic instability characteristics of the RD-CNTRC plates. The reduced computational effort allows the design phase to be supported in selecting parameters when designing RD-CNTRC plates with stability and vibration requirements.
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    Effect of Cutout on the Stability and Failure of Laminated Composite Cylindrical Panels Subjected to In-Plane Pulse Loads
    (World Scientific, 2022) Watts, Gaurav; Kumar, Rajesh; Patel, Shuvendu Narayan
    In this investigation, the nonlinear dynamic buckling analysis and the failure analysis of laminated composite cylindrical (LCC) panel with different shapes of cutouts under the action of rectangular in-plane pulse loads are performed in the finite element framework. Cross-ply laminates which are balanced symmetric are considered in the investigation. The first ply failure load (FPFL) of the panel is evaluated and checked whether it occurs before the nonlinear dynamic buckling phenomenon considering Tsai–Wu failure criterion. Convergence and validation studies are undertaken, and the results are compared with those from the existing literature. The effects of loading duration, cutout area and cutout geometry on the panel are investigated in detail and results are reported. The results indicate that for the panel with cutout, its dynamic buckling load (DBL), in certain cases, compared to the static buckling load (SBL), can be lower even if the loading duration is half of its first natural period. Additionally, the vibration and the static buckling analyses of the panels are carried out as and when required.
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    Postbuckling and postbuckled vibration behaviour of imperfect trapezoidal sandwich plates with FG-CNTRC face sheets under nonuniform loadings
    (Elsevier, 2022-08) Watts, Gaurav; Kumar, Rajesh; Patel, Shuvendu Narayan
    The present work investigates the postbuckling, and postbuckled vibration behaviour of initially imperfect trapezoidal sandwich plates with functionally graded carbon nanotube reinforced composite (FG-CNTRC) face sheets and FG porous metal foam core under the influence of non-uniform edge compression. The plate's kinematic assumptions are based on a refined higher order theory and the strain-displacement relations include von Karman assumptions for geometrical nonlinearity. The weak form of governing equations derived using Hamilton's principle is transformed into a discretized form of algebraic equations using the element free Galerkin (EFG) method in conjunction with moving kriging (MK) interpolation functions. The pre-buckling stresses are determined using static analysis to evaluate accurate critical buckling loads. Modified Riks technique is used to trace nonlinear equilibrium paths. Parametric studies include the effect of CNT distribution in face sheets, porosity distribution in the core layer and edge loading conditions on the nonlinear stability and vibration behaviour of sandwich plates. New results on trapezoidal sandwich plates with initial imperfections, hitherto not found in the literature, are presented for the first time, which can be used as benchmark solutions for further research.