The stability of composite conical shells covered by carbon nanotube-reinforced coatings under external pressures
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O R I G I NA L PA P E R
A. H. Sofiyev
· R. P. Bayramov · S. H. Heydarov
The stability of composite conical shells covered by carbon nanotube-reinforced coatings under external pressures
Received: 19 March 2020 / Revised: 25 June 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract In this study, the stability of sandwich conical shells covered by functionally graded and uniform distributed carbon nanotube-reinforced composite coatings under external pressures is carried out. The mechanical properties of the carbon nanotube and matrix are assumed to be graded through the thickness of the coatings via three types of grading rule. The basic relationships and stability equations of sandwich conical shells reinforced by carbon nanotubes are obtained employing the modified Donnell-type shell theory and generalized first-order shear deformation theory. The Galerkin procedure is employed to define expressions for the external buckling pressures. For the accuracy of the proposed formulation, the results are compared with the results that are published in the literature. It follows a systematic study aimed at checking the sensitivity of the structural response to the type of pattern and the volume fraction of carbon nanotubes in the composite coatings.
1 Introduction The sandwich structural elements are widely used in many areas, from the aerospace industry to the marine, automotive, and construction industries, due to their low weight, high strength/weight ratio, and durability compared to conventional materials. The formation of sandwich structures was carried out from homogeneous composite materials in the early periods. The first studies on the design, modeling, production technologies, and areas of application for sandwich structures are presented in Ref. [1]. The sharp differences in the material properties of the layers constituting the sandwich structures which are subjected to various external pressures and thermal influences lead to delamination of the layers, which leads to the destruction of the sandwich structures [2]. The many years of intense efforts by materials scientists and designers have led to a significant reduction in the delamination of sandwich structures by the production and application of new generation composites. One of the most popular composite materials of recent years are the nano-materials. The carbon nanotubes (CNTs) are the most extensively researched nanoscale materials that were experimentally discovered by Iijima [3] in 1991. Due to the unique characteristics of CNTs from various mechanical, electrical, and thermal points of view, they are considered an ideal and promising candidate for polymer hardening, and the potentialities of CNT-based composites have received wide attention in recent years [4–8]. Shen [9] proposed a new and effective model for solving various problems by creating the concept of carbon nanotube-based functionally graded composite shells. Kwon et al. [10] fabricated a CNT-reinforced composite aluminum matrix using powder metallurgy in th
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