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Journal ArticleDOI

Nonlinear axisymmetric dynamic buckling of functionally graded graphene reinforced porous nanocomposite spherical caps

17 Jan 2021-Mechanics of Advanced Materials and Structures (Taylor & Francis)-Vol. 28, Iss: 2, pp 127-140
TL;DR: In this article, the axisymmetric dynamic snap-through buckling of graphene platelets reinforced porous nanocomposite spherical caps subjected to a suddenly applied external pressure load is focused.
Abstract: Here, the axisymmetric dynamic snap-through buckling of graphene platelets (GPLs) reinforced porous nanocomposite spherical caps subjected to a suddenly applied external pressure load is focused us...
Citations
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Journal ArticleDOI
TL;DR: In this paper, a three variable refined shear deformation theory was developed to analyze the free vibration and bending behavior of porous doubly curved shallow shells subjected to uniform and sinusoidal pressure.

46 citations

Journal ArticleDOI
TL;DR: In this article, the impact response of shear deformable sandwich cylindrical shells composed of two face layers and a functionally graded (FG) porous core was investigated, and the mass density and elastic moduli of FG were investigated.
Abstract: The impact response of shear deformable sandwich cylindrical shells composed of two face layers and a functionally graded (FG) porous core is investigated. The mass density and elastic moduli of FG...

38 citations

Journal ArticleDOI
TL;DR: In this paper, the lower bound buckling pressure of thin-walled spherical shells under external pressure was evaluated using empirical knockdown factors, based on experimental results from the beginning of the 20th century and have been shown to be very conservative for modern shell structures.
Abstract: For the design of thin-walled spherical shells under external pressure empirical knockdown factors are applied. These knockdown factors are based on experimental results from the beginning of the 20th century and have been shown to be very conservative for modern shell structures. In order to determine less conservative and physically based knockdown factors for the design of spherical shells, different analytical and numerical design approaches have been developed. In this paper common as well as new shell design approaches are presented in detail and evaluated regarding the lower-bound buckling pressure. Among these design approaches are the reduced stiffness method, measured geometric imperfections and perturbation approaches. Important analysis and modeling details of each design approach are described, and test examples are given and validated. Advantages and disadvantages of each approach are listed, and design recommendations are given. Practical shell buckling design examples are demonstrated by means of a tori-spherical bulkhead and a deep-sea spherical pressure hull. In addition, a collection of about 700 experimental knockdown factors for spherical shells under external pressure is given in the Elsevier repository.

29 citations

Journal ArticleDOI
TL;DR: In this paper, a numerical design approach for deep spherical shells under external pressure is presented, which leads to significantly improved critical load estimations in comparison to lower-bounds obtained empirically.

27 citations


Cites background from "Nonlinear axisymmetric dynamic buck..."

  • ...Further applications for spherical shell like structures are lattice domes [5], actuators [6], carbon nanospheres [7], nanocomposite spherical caps [8], biopolymer spherical shells [9], plexiglass shields [10], underwater robots [11] and concave bottom closures of elevated shell-of-revolution liquid-containment tanks [12]....

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Journal ArticleDOI
TL;DR: In this paper, the authors implemented hygrothermo-mechanical nonlinear analysis of curved thin and moderately thick shallow panels, in which Functionally Graded Materials (FGMs) are employed.
Abstract: This study is dedicated to implement hygro-thermo-mechanical nonlinear analysis of curved thin and moderately thick shallow panels, in which Functionally Graded Materials (FGMs) are employed throug...

24 citations

References
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Journal ArticleDOI
Sumio Iijima1, Toshinari Ichihashi1
17 Jun 1993-Nature
TL;DR: In this article, the authors reported the synthesis of abundant single-shell tubes with diameters of about one nanometre, whereas the multi-shell nanotubes are formed on the carbon cathode.
Abstract: CARBON nanotubes1 are expected to have a wide variety of interesting properties. Capillarity in open tubes has already been demonstrated2–5, while predictions regarding their electronic structure6–8 and mechanical strength9 remain to be tested. To examine the properties of these structures, one needs tubes with well defined morphologies, length, thickness and a number of concentric shells; but the normal carbon-arc synthesis10,11 yields a range of tube types. In particular, most calculations have been concerned with single-shell tubes, whereas the carbon-arc synthesis produces almost entirely multi-shell tubes. Here we report the synthesis of abundant single-shell tubes with diameters of about one nanometre. Whereas the multi-shell nanotubes are formed on the carbon cathode, these single-shell tubes grow in the gas phase. Electron diffraction from a single tube allows us to confirm the helical arrangement of carbon hexagons deduced previously for multi-shell tubes1.

8,018 citations

Journal ArticleDOI
John Banhart1
TL;DR: The possibilities for manufacturing metal foams or other porous metallic structures are reviewed in this article, where various manufacturing processes are classified according to the state of matter in which the metal is processed, such as solid, liquid, gaseous or ionised.

3,294 citations

Journal ArticleDOI
TL;DR: The Halpin-Tsai equations are based upon the self-consistent micromechanics method developed by Hill as discussed by the authors. But they are not suitable for semi-crystalline polymers.
Abstract: The Halpin-Tsai equations are based upon the “self-consistent micromechanics method” developed by Hill. Hermans employed this model to obtain a solution in terms of Hill's “reduced moduli”. Halpin and Tsai have reduced Hermans' solution to a simpler analytical form and extended its use for a variety of filament geometries. The development of these micromechanic's relationships, which form the operational bases for the coniposite analogy of Halpin and Kardos for semi-crystalline polymers, are reviewed herein.

2,609 citations

Journal ArticleDOI
03 Dec 2009-ACS Nano
TL;DR: Graphene platelets significantly out-perform carbon nanotube additives in terms of mechanical properties enhancement, and may be related to their high specific surface area, enhanced nanofiller-matrix adhesion/interlocking arising from their wrinkled (rough) surface, as well as the two-dimensional geometry of graphene platelets.
Abstract: In this study, the mechanical properties of epoxy nanocomposites with graphene platelets, single-walled carbon nanotubes, and multi-walled carbon nanotube additives were compared at a nanofiller weight fraction of 0.1 ± 0.002%. The mechanical properties measured were the Young’s modulus, ultimate tensile strength, fracture toughness, fracture energy, and the material’s resistance to fatigue crack propagation. The results indicate that graphene platelets significantly out-perform carbon nanotube additives. The Young’s modulus of the graphene nanocomposite was ∼31% greater than the pristine epoxy as compared to ∼3% increase for single-walled carbon nanotubes. The tensile strength of the baseline epoxy was enhanced by ∼40% with graphene platelets compared to ∼14% improvement for multi-walled carbon nanotubes. The mode I fracture toughness of the nanocomposite with graphene platelets showed ∼53% increase over the epoxy compared to ∼20% improvement for multi-walled carbon nanotubes. The fatigue resistance resu...

2,367 citations

Journal ArticleDOI
TL;DR: In this paper, the phonon spectra of graphene were calculated as a function of uniaxial tension by density functional perturbation theory to assess the first occurrence of phonon instability on the strain path.
Abstract: Graphene-based $s{p}^{2}$-carbon nanostructures such as carbon nanotubes and nanofibers can fail near their ideal strengths due to their exceedingly small dimensions. We have calculated the phonon spectra of graphene as a function of uniaxial tension by density functional perturbation theory to assess the first occurrence of phonon instability on the strain path, which controls the strength of a defect-free crystal at $0\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Uniaxial tensile strain is applied in the $x$ (nearest-neighbor) and $y$ (second nearest-neighbor) directions, related to tensile deformation of zigzag and armchair nanotubes, respectively. The Young's modulus $E=1050\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ and Poisson's ratio $\ensuremath{ u}=0.186$ from our small-strain results are in good agreement with previous calculations. We find that in both $x$ and $y$ uniaxial tensions, phonon instabilities occur near the center of the Brillouin zone, at (${\ensuremath{\epsilon}}_{xx}=0.194$, ${\ensuremath{\sigma}}_{xx}=110\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, ${\ensuremath{\epsilon}}_{yy}=\ensuremath{-}0.016$) and (${\ensuremath{\epsilon}}_{yy}=0.266$, ${\ensuremath{\sigma}}_{yy}=121\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, ${\ensuremath{\epsilon}}_{xx}=\ensuremath{-}0.027$), respectively. Both soft phonons are longitudinal elastic waves in the pulling direction, suggesting that brittle cleavage fracture may be an inherent behavior of graphene and carbon nanotubes at low temperatures. We also predict that a phonon band gap will appear in highly stretched graphene, which could be a useful spectroscopic signature for highly stressed carbon nanotubes.

1,370 citations