BITS Faculty Publications

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Author: search.filters.author.Kumar, RajeshSubject: search.filters.subject.Carbon nanotubes (CNTs)

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    Study on bending characteristics of CNT-reinforced metal Timoshenko composite porous beam exposed to transverse patch loading
    (Sage, 2025-03) Kumar, Rajesh
    Bending characteristics of porous composite beams reinforced by carbon nanotubes (CNTs) under localized transverse loading is examined in the current study. Initially, single-walled carbon nanotubes (SW-CNTs) are utilized as nanofillers within a metal matrix to enhance the beam’s mechanical properties. The effective mechanical properties of the beam are assessed using the Eshelby-Mori-Tanaka method. Next, the porosity of the beam is modeled as being distributed layer-by-layer through the beam’s thickness, either uniformly or in a non-uniform manner, with three distinct distribution types considered: uniform, symmetric non-uniform, and asymmetric non-uniform. The beam is mathematically modeled using theory of Timoshenko beam combining nonlinearity of von-Kármán. The governing nonlinear algebraic equations are derived from the principle of minimizing total potential energy. These equations are then simplified using the Galerkin method and solved implementing Newton-Raphson technique to determine the load-deformation path. Finally, the study is performed using different parameters to analyze their impact on the bending behavior of CNT-metal reinforced porous composite beams. This includes the mass fraction of SW-CNTs, porosity distribution types, agglomeration effects of CNTs, porosity coefficients, aspect ratio, types of transverse loading, and different metal matrices.
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    Semianalytical Development of Dynamic Instability and Response of a Multiscale Laminated Hybrid Composite Plate
    (ASCE, 2021-01) Patel, Shuvendu Narayan; Kumar, Rajesh
    The use of carbon nanotubes (CNTs) in augmenting the mechanical properties of fiber-reinforced laminated composites is a fact. In this paper, the semianalytical studies on the dynamic instability behavior and linear and nonlinear responses of a randomly distributed CNT and fiber-reinforced interlamina hybrid composite (CNTFRHC) plate with and without damping under time-dependent in-plane uniaxial uniform compression loading are presented. Each lamina of the laminate is made of multiscale materials such as CNT/polymer/fiber. The effective mechanical properties of the lamina are estimated in two steps. First, the Eshelby–Mori–Tanaka technique is used to compute the effective mechanical properties of randomly distributed CNTs in a polymer matrix (i.e., CNT-embedded matrix). Second, the effective mechanical properties of the CNT-embedded matrix reinforced with fiber (either carbon or glass) are estimated by using various homogenization techniques. The plate is modeled by using higher-order shear deformation theory (HSDT) and von Kármán nonlinearity. Governing partial differential equations of the CNTFRHC plate are obtained by Hamilton’s principle and reduced to Mathieu–Hill equations by using the Galerkin method. Mathieu–Hill equations are solved by the Bolotin method to trace the boundaries of the instability region corresponding periods and . Finally, the influence of different parameters such as CNT agglomerations, CNT mass fraction, edge-to-thickness ratio, compression preloading, boundary conditions, and damping on the dynamic instability region of the CNTFRHC plates are studied in detail. Numerical results provide useful insights into the selection of parameters with different combinations for the desired design of the CNTFRHC plate against instability. Furthermore, to know the characteristics of the instability region of a CNTFRHC plate such as the existence of beats, dependence on geometric nonlinearity, and forcing frequency for which the linear and nonlinear responses with and without damping in both stable and unstable regions are presented.
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    Influence of Carbon Nanotubes on Stability and Vibration Characteristics of Plates and Panels in Thermal Environment: A Review
    (Springer, 2023-07) Kumar, Rajesh
    Laminated composites became a cutting-edge material in the twentieth century due to their extensive use in engineering, owing to their high strength and lightweight characteristics. Composites are manufactured with polymers and reinforced with fibers such as glass fiber, carbon fiber, Kevlar fiber, and many more. Delamination has been found to be a significant problem in composite materials, and it has the potential to cause catastrophic failure through brittle failure. To delay such events in polymer composites, carbon-based nanoparticles have been widely added to reinforce the polymer, resulting in an improvement in the strength of composites. After 1991, the development of carbon nanotubes (CNTs) revolutionized the plastic composite industry due to its versatile characteristics. CNT, whose strength is 100 times higher than that of steel, can reinforce polymers and enhance the mechanical strength of composites. The present study focuses on reviewing the published literature to provide an insight view for readers to predict the stability and vibration characteristics of CNT-reinforced composite panels. It also discusses the influence of temperature rise, functional gradation, volume fraction, and agglomeration effect in case of randomly distributed CNTs in composite plates/panels. The research gaps are identified at the end that may help readers understand the voids in this field of research.