Gotowe bibliografie tematyczne / Finite Graphene Sheets

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Gotowa bibliografia na temat „Finite Graphene Sheets”

Autor: Grafiati

Data publikacji: 6 września 2023

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Artykuły w czasopismach na temat "Finite Graphene Sheets"

Ahmadi, M., R. Ansari i S. Rouhi. "Investigating the thermal conductivity of concrete/graphene nanocomposite by a multi-scale modeling approach". International Journal of Modern Physics B 32, nr 14 (5.06.2018): 1850171. http://dx.doi.org/10.1142/s0217979218501710.

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In this paper, a multi-scale modeling approach is used to study the effect of adding graphene sheets to concrete matrix on the thermal conductivity of the concrete. By computing the thermal conductivity of the graphene along the armchair and zigzag directions using molecular dynamics (MO) simulations, it is shown that the graphene sheets have orthotropic thermal behavior. Therefore, at the upper scale, in which the finite element (FE) method is used to obtain the thermal conductivity of the concrete/graphene nanocomposites, the graphene sheets are considered as orthotropic continuous sheets. It is shown that the improvement of the concrete thermal conductivity by adding the graphene sheets is directly related to the graphene sheet volume percentage and cross-sectional dimensions.

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Zhen, Cai Ru, Yu Li Chen, Chuan Qiao i Qi Jun Liu. "Atomistic Simulation on Buckling Behavior of Monolayer Graphene". Advanced Materials Research 1095 (marzec 2015): 35–38. http://dx.doi.org/10.4028/www.scientific.net/amr.1095.35.

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The buckling behavior of monolayer graphene sheets with simple-supported, clamped-free and clamped-clamped boundary conditions is investigated by the atomic-scale finite method (AFEM). The initial static equilibrium state of monolayer graphene sheet is obtained in the simulation as a waved configuration which is close to the real graphene observed in experiments. With the increase of compressive displacement, the force displays three stages: linear increasing, nonlinear increasing and decreasing slowly after a sudden drop. Different from the prediction by classical theory, the critical buckling loads of graphene sheets with different boundary conditions are similar, which is attributed to the initial waved configuration of the monolayer graphene sheets.

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Petrushenko, Igor K. "DFT Study on Adiabatic and Vertical Ionization Potentials of Graphene Sheets". Advances in Materials Science and Engineering 2015 (2015): 1–7. http://dx.doi.org/10.1155/2015/262513.

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Adiabatic and vertical ionization potentials (IPs) of finite-size graphene sheets as a function of size were determined by using density functional theory. In the case of graphene a very moderate gap between vertical and adiabatic IPs was observed, whereas for coronene molecule as a model compound these values differ considerably. The ionization process induces large changes in the structure of the studied sheets of graphene; “horizontal” and “vertical” bond lengths have different patterns of alternation. It was also established that the HOMO electron density distribution in the neutral graphene sheet affects its size upon ionization. The evolution of IPs of graphene sheets towards their work functions was discussed.

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Kazemi, Seyedeh Alieh, Sadegh Imani Yengejeh i Andreas Öchsner. "On the Modeling of Eigenmodes and Eigenfrequencies of Carbon Graphene Sheets under the Influence of Vacancy Defects". Journal of Nano Research 38 (styczeń 2016): 101–6. http://dx.doi.org/10.4028/www.scientific.net/jnanor.38.101.

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The vibrational behavior of defected graphene sheets was investigated via finite element analysis. The simulations were carried out for perfect and imperfect nanosheets. This study was conducted to examine the influence of vacant sites on these nanostructures. In the current study, a graphene sheet is considered as a space frame. The natural frequency and corresponding mode shapes of the perfect and defective nanosheets were obtained and compared. Results are presented as diagrams stating the natural frequency of graphene sheets with respect to the amount of vacancy defects. The results indicate that the natural frequency of nanosheets reduced by introducing atomic defects to the configuration of these nanomaterials. Such impurities lower the vibrational stability of graphene sheets.

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Wang, Xiunan, Yi Liu, Jingcheng Xu, Shengjuan Li, Fada Zhang, Qian Ye, Xiao Zhai i Xinluo Zhao. "Molecular Dynamics Study of Stability and Diffusion of Graphene-Based Drug Delivery Systems". Journal of Nanomaterials 2015 (2015): 1–14. http://dx.doi.org/10.1155/2015/872079.

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Graphene, a two-dimensional nanomaterial with unique biomedical properties, has attracted great attention due to its potential applications in graphene-based drug delivery systems (DDS). In this work graphene sheets with various sizes and graphene oxide functionalized with polyethylene glycol (GO-PEG) are utilized as nanocarriers to load anticancer drug molecules including CE6, DOX, MTX, and SN38. We carried out molecular dynamics calculations to explore the energetic stabilities and diffusion behaviors of the complex systems with focuses on the effects of the sizes and functionalization of graphene sheets as well as the number and types of drug molecules. Our study shows that the binding of graphene-drug complex is favorable when the drug molecules and finite graphene sheets become comparable in sizes. The boundaries of finite sized graphene sheets restrict the movement of drug molecules. The double-side loading often slows down the diffusion of drug molecules compared with the single-side loading. The drug molecules bind more strongly with GO-PEG than with pristine graphene sheets, demonstrating the advantages of functionalization in improving the stability and biocompatibility of graphene-based DDS.

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Dobrescu, Oana-Ancuta, i M. Apostol. "Tight-binding approximation for bulk and edge electronic states in graphene". Canadian Journal of Physics 93, nr 5 (maj 2015): 580–84. http://dx.doi.org/10.1139/cjp-2014-0313.

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The tight-binding approximation is employed here to investigate electronic bulk and edge (“surface”) states in semi-infinite graphene sheets and graphene monolayer ribbons with various edge terminations (zigzag, horseshoe, and armchair edges). It is shown that edge states do not exist for a uniform hopping (transfer) matrix. The problem is generalized to include edge elements of the hopping matrix distinct from the infinite-sheet (“bulk”) ones. In this case, semi-infinite graphene sheets with zigzag or horseshoe edges exhibit edge states, while semi-infinite graphene sheets with armchair edges do not. The energy of the edge states lies above the (zero) Fermi level. Similarly, symmetric graphene ribbons with zigzag or horseshoe edges exhibit edge states, while ribbons with asymmetric edges (zigzag and horseshoe) do not. It is also shown how to construct the “reflected” solutions (bulk states) for the intervening equations with finite differences both for semi-infinite sheets and ribbons.

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REDDY, C. D., S. RAJENDRAN i K. M. LIEW. "EQUIVALENT CONTINUUM MODELING OF GRAPHENE SHEETS". International Journal of Nanoscience 04, nr 04 (sierpień 2005): 631–36. http://dx.doi.org/10.1142/s0219581x05003528.

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Carbon nanotubes have drawn tremendous interest due to their excellent mechanical and electronic properties. Carbon nanotubes have a similar molecular structure as that of graphene sheets. Hence, characterization of mechanical properties of graphene sheet based on equivalent continuum modelling is of considerable importance. Our initial studies are carried out on a single carbon ring/cell. The ring is then modelled as a truss (finite) element assemblage and equivalent Young's modulus is computed for a few fundamental modes. Next, these studies have been extended to model graphene sheet as a planar continuum to determine the mechanical properties (Young's modulus, shear modulus and Poisson's ratio) for typical modes of deformation. Further research is in progress to investigate how this set of different values can be integrated together towards a meaningful continuum characterization of the inherent discrete structure.

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Bocko, J., i P. Lengvarský. "Elastic modulus of defected graphene sheets". IOP Conference Series: Materials Science and Engineering 1199, nr 1 (1.11.2021): 012021. http://dx.doi.org/10.1088/1757-899x/1199/1/012021.

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Abstract In this paper, the elastic modulus of single-layered graphene sheets (SLGSs) with and without defects is investigated using the finite element method. The SLGSs with two chiralities (armchair and zigzag) are modeled by beam elements. At first, the SLGSs without defects are investigated then the carbon atoms and corresponding beam elements are removed and the elastic modulus of SLGSs is determined. The increasing number of defects apparently decreased the elastic modulus of graphene sheets.

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Bocko, Jozef, i Pavol Lengvarský. "Buckling analysis of graphene nanosheets by the finite element method". MATEC Web of Conferences 157 (2018): 06002. http://dx.doi.org/10.1051/matecconf/201815706002.

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The paper is devoted to the problems related to buckling analysis of graphene sheets without and with vacancies in the structure under different boundary conditions. The analysis was performed by the classical numerical treatment – the finite element method (FEM). The graphene sheets were modelled by beam elements. Interatomic relations between carbon atoms in the structure were represented by the beams connecting individual atoms. The behaviour of the beam as structural element was based on the properties that were established from relations of molecular mechanics. The vacancies in single layer graphene sheets (SLGSs) were created by elimination of randomly chosen atoms and corresponding beam elements connected to the atoms in question. The computations were accomplished for different percentage of atom vacancies and the results represent an obvious fact that the critical buckling force decreases for increased percentage of vacancies in the structure. The numerical results are represented in form of graphs.

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Yengejeh, Sadegh Imani, Seyedeh Alieh Kazemi, Oleksandr Ivasenko i Andreas Öchsner. "Simulations of Graphene Sheets Based on the Finite Element Method and Density Functional Theory: Comparison of the Geometry Modeling under the Influence of Defects". Journal of Nano Research 47 (maj 2017): 128–35. http://dx.doi.org/10.4028/www.scientific.net/jnanor.47.128.

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In the present research, imperfect graphene sheets were generated and their vibrational property was studied via finite element analysis. The effect of vacant sites in the arrangement of these nano-structures was examined. The fundamental frequency of the defect free and imperfect nano-sheets was acquired based on two different approaches. The first approach was a pure finite element simulation. The second approach for comparison purpose was a recently reported refined finite element simulation at which the vicinity of a defect was first evaluated according to the density functional theory (DFT) and then the refined geometry was implemented into a finite element model. The findings of this research show that the fundamental frequency of graphene sheets decreases by presenting microscopic imperfection to the formation of these nano-materials. In addition, it was pointed out that the geometry based on the more precise DFT simulations gives a higher decrease in the fundamental frequency of the sheets for all considered cases.

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Rozprawy doktorskie na temat "Finite Graphene Sheets"

Brujas, Marco Antonio. "Análise numérica e experimental dos efeitos da não-uniformidade da espessura em cascas finas cilíndricas rotativas". Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/3/3144/tde-08082007-165939/.

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Cascas cilíndricas circulares com uma pequena variação de espessura ao longo de seu comprimento, quando submetidas à rotação, apresentam em alguns casos, deslocamentos elásticos de sua superfície externa, tendendo a uma forma de um oval. O objetivo deste trabalho é estabelecer a relação entre a variação de espessura das cascas cilíndricas com a sua deformação devida às forças centrífugas medida durante a rotação utilizando-se dois enfoques, um experimental e outro numérico, no caso o método de elementos finitos (MEF). As cascas cilíndricas estudadas tiveram sua espessura de parede medidas por meio de aparelho de ultra-som, mas por serem fabricadas em ferro fundido cinzento, as suas lamelas de grafita atuam como refletores, o que torna a medição imprecisa. Os resultados da análise numérica encontrados se relacionam bem com os experimentais de maneira qualitativa, mas divergem na forma quantitativa. Modelos de cascas com variação de espessura imposta também foram criados e analisados usando-se o método de elementos finitos de forma a se avaliar o comportamento da casca cilíndrica sob diversas configurações de distribuição da variação da espessura. Sugere-se a pesquisa de novas tecnologias para medições por ultra-som de peças fabricadas de ferro fundido com grafita lamelar. Neste trabalho, a medição da forma oval foi feita utilizando-se sensores de proximidade do tipo \"eddy-current\".
Circular cylindrical shells with small thickness variations along their body, when submitted to rotation, present, in some cases, elastic displacements of their outside surface induced by centrifugal forces leading to final oval like shapes. The main purpose of this study is to establish relationships between thickness variation of the cylindrical shells with their measured deformation during the rotation, due to centrifugal forces, using two approaches, one experimental and the other one numerical, in the latter case the finite element method (FEM). The studied cylindrical shells had their wall thickness measured by means of an ultrasound device. The used material is flake graphite cast iron (gray cast iron). The graphite flakes act as reflectors, what makes such measurements imprecise. The numerical results found are satisfactory in a qualitative way, but they disagree in the quantitative form. Shell models with theoretical imperfections also were created and analyzed using the finite element method in order to evaluate the behavior of the cylindrical shell under several configurations of distribution of the shell thickness variation. Further research is necessary on new technologies to measure the thickness of pieces manufactured of flake graphite cast iron. In this research, the oval shape measurements were done by means of eddy-current proximity sensors.

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Khare, Ojasvi. "Edge States and Effects of Disorder in Finite Graphene Sheets". Thesis, 2017. https://etd.iisc.ac.in/handle/2005/4160.

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The thesis endeavours to theoretically understand electronic properties of nite trapezoidal shaped graphene sheets, and understand zero energy edge states. The motivation for this thesis is recent experimental work at Low Temperature Nano-electronics Laboratory under Prof. Arindam Ghosh[ ?]. This work sys-tematically tries to understand graphene, a two dimensional material, and it's confinement in spacial dimensions. In Part I, we start with analytical study of bulk graphene with various hoppings in a tight-binding formulation and its band structure. Then we confine graphene in one-dimension to form semi-in finite graphene nanoribbons and numerically determine its energy spectra and wave-functions for sites along the finite direction. In Part II, graphene is confined in both spacial dimensions and starting from simplest case of finite rectangular sheet, we move on to the two different ways in which graphene can be torn. Here, numerical studies were done to determine the density of states and local density of states. Finally Parts III and IV are devoted to the study of disorders and how various kinds of disorders can be introduced in the system and their effect in localising the wave-functions along the edges.

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Hsu, Ting-Wei, i 許廷瑋. "Finite-Difference Time-Domain Method with Virtual Absorbing Layer to Simulate Klein Tunneling on a Graphene Sheet". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/2wjap6.

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碩士
國立臺灣大學
電信工程學研究所
102
The finite-di ffrence time-domain(FDTD) method is applied to solve the Dirac-like equation of a graphene sheet. A virtual absorbing layer (VAL) is proposed to achieve low reflection of wave function at the boundary of a graphene sheet. Empirical parameters are tuned to optimize the performance of the VAL. The Klein tunneling effects on a graphene sheet are simulated to confirm the effectiveness of this FDTD scheme and the VAL.

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Książki na temat "Finite Graphene Sheets"

Gotsis, Pascal K. Progressive fracture of fiber composite thin shell structures under internal pressure and axial loads. [Washington, DC]: National Aeronautics and Space Administration, 1996.

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Gotsis, Pascal K. Progressive fracture of fiber composite thin shell structures under internal pressure and axial loads. [Washington, DC]: National Aeronautics and Space Administration, 1996.

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United States. National Aeronautics and Space Administration., red. Buckling and damage resistance of transversely-loaded composite shells. [Washington, DC: National Aeronautics and Space Administration, 1998.

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Streszczenia konferencji na temat "Finite Graphene Sheets"

Sakhaee-Pour, A., M. T. Ahmadian i A. Vafai. "Nanoscale Vibrational Behavior of Single-Layered Graphene Sheets". W ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-43233.

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Molecular structural mechanics approach is implemented to investigate vibrational behavior of single-layered graphene sheets. By using the atomistic modeling, mode shapes and natural frequencies are obtained. Vibration analysis is performed under different chirality and boundary conditions. Numerical results from the finite element technique are applied to develop empirical equations via a statistical multiple nonlinear regression model. With the proposed empirical equations, fundamental frequencies of single-layered graphene sheets under considered boundary conditions can be predicted within 3 percent accuracy.

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Alzebdeh, Khalid I. "Evaluation of Effective Elastic Mechanical Properties of Graphene Sheets". W ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-87211.

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The mechanical behaviour of a single-layer nanostructured graphene sheet is investigated using an atomistic-based continuum model. This is achieved by equating the stored energy in a representative unit cell for a graphene sheet at atomistic scale to the strain energy of an equivalent continuum medium under prescribed boundary conditions. Proper displacement-controlled (essential) boundary conditions which generate a uniform strain field in the unit cell model are applied to calculate one elastic modulus at a time. Three atomistic finite element models are adopted with an assumption that force interactions among carbon atoms can be modeled by either spring-like or beam elements. Thus, elastic moduli for graphene structure are determined based on the proposed modeling approach. Then, effective Young’s modulus and Poisson’s ratio are extracted from the set of calculated elastic moduli. Results of Young’s modulus obtained by employing the different atomistic models show a good agreement with the published theoretical and numerical predictions. However, Poisson’s ratio exhibits sensitivity to the considered atomistic model. This observation is supported by a significant variation in estimates as can be found in the literature. Furthermore, isotropic behaviour of in-plane graphene sheets was validated based on current modeling.

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Bouzianas, Georgios D., Nikolaos V. Kantartzis i Theodoros D. Tsiboukis. "RCS analysis of finite graphene sheets through an enhanced frequency-dependent FDTD method". W 2012 6th European Conference on Antennas and Propagation (EuCAP). IEEE, 2012. http://dx.doi.org/10.1109/eucap.2012.6206382.

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Hemmasizadeh, Ali, Mojtaba Mahzoon, Vahid Yavari i Rasoul Khandan. "A Semi-Analytical Method for Developing the Equivalent Continuum Model of a Single Layer Graphene Sheet". W ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-67537.

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A semi-analytical method is presented to develop the equivalent continuum model for a single-layered graphene sheet. This method integrates molecular dynamics method as an exact numerical solution with theory of shell as an analytical method. The force-depth results obtained from molecular dynamics (MD) simulation of nano-indentation of a single graphene sheet are compared with the formulation for large deflection of circular plates loaded at the centre. As a result, the effective Young’s modulus and mechanical thickness of the sheet wall are independently obtained. The validity of this new approach is verified by comparing finite element modeling of nano-indentation of a single graphene sheet with molecular dynamics results available in the literature. Presented results demonstrate that the proposed method could provide a valuable tool for studying the mechanical behavior of single-layered graphene sheets, as well as efficiency of continuum theory in nano-structured material.

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Avery, John L., Manickam Narayanan i Bhavani V. Sankar. "Compressive Failure of Debonded Sandwich Beams". W ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0380.

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Abstract Compression tests were performed on debonded sandwich beams made of graphite/epoxy face-sheets and aramid fiber honeycomb core. The sandwich beams were manufactured using a vacuum bagging process. The face-sheet and the sandwich beam were co-cured, thus the excess resin from the graphite/epoxy prepregs was used to bond the face-sheet and the core. Delamination between one of the face sheets and the core was introduced by using a Teflon® layer during the curing process. Axial compression tests were performed to determine the ultimate load carrying capacity of the debonded beams. Double Cantilever Beam tests were performed to determine the fracture toughness of the face-sheet/core interface. It was concluded that linear buckling analysis was inadequate for predicting the ultimate loads. A post-buckling analysis was carried out using a nonlinear plane finite element model of the sandwich beam. The ultimate loads predicted by the finite element model were reasonably good for specimens with long delaminations.

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Wallace, Brian T., Bhavani V. Sankar i Peter G. Ifju. "Delamination Suppression in Sandwich Beams Using Translaminar Reinforcements". W ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0130.

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Abstract The present study is concerned with translaminar reinforcement in a sandwich beam for preventing buckling of a delaminated face-sheet under axial compression. Graphite/epoxy pins are used as reinforcement in the thickness direction of sandwich beams consisting of graphite/epoxy face-sheets and a Aramid honeycomb core. Compression tests are performed to understand the effects of the diameter of the reinforcing pins and reinforcement spacing on the ultimate compressive strength of the delaminated beams. A finite element analysis is performed to understand the effects of translaminar reinforcement on the critical buckling loads and post-buckling behavior of the sandwich beam under axial compression.

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Lu, Xiaoxing, i Zhong Hu. "Evaluation of Mechanical Behaviors of Single-Walled Carbon Nanotubes by Finite Element Analysis". W ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-37766.

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Based on molecular mechanics, a three-dimensional finite element model for armchair, zigzag and chiral single-walled carbon nanotubes (SWCNTs) has been developed, in which the carbon nanotubes (CNTs), when subjected to load, behave like space-frame structures. The bending stiffness of the graphite layer has been considered. The potentials associated with the atomic interactions within a CNT were evaluated by the strain energies of beam elements which serve as structural substitutions of covalent bonds. The out-of-plane deformation (inversion) of the bonds was distinguished from the in-plane deformation by considering an elliptical cross-section for the beam elements. The elastic moduli of beam elements are determined by using a linkage between molecular and continuum mechanics. A closed form solution of the sectional properties of the beam element was derived analytically and verified through the analysis of rolling a graphite sheet into a carbon nanotube. This method was validated by its application to a graphene model, and Young’s modulus of the model was found, showing agreement with the known values of graphite. Modeling of the elastic deformation of SWCNTs reveals that Young’s moduli and the shear modulus of CNTs vary with the tube diameter and are affected by their helicity. With increasing tube diameter, Young’s moduli of both armchair and zigzag CNTs are increasing monotonically and approaching to the Young’s modulus of graphite, which are in agreement with the existing theoretical and experimental results. The rolling energy per atom was computed by finite element analysis. By comparing mechanical properties with circular cross section models, it is found that the computational results of the proposed elliptical cross-section model are closer to the results from the atomistic computations. The proposed model is valid for problems where the effect of local bending of the graphite layer in a CNT is significant. This research work shows that the proposed finite element model may provide a valuable tool for studying the mechanical behaviors of CNTs and their integration in nano-composites.

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Veedu, Vinod P., Davood Askari i Mehrdad N. Ghasemi-Nejhad. "Analytical and Numerical Predictions of Thermoelastic Properties of Carbon Single-Walled Nanotubes". W ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-80256.

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The objective of this paper is to develop constitutive models to predict thermoelastic properties of carbon single-walled nanotubes using analytical, asymptotic homogenization, and numerical, finite element analysis, methods. In our approach, the graphene sheet is considered as a non-homogeneous network shell layer which has zero material properties in the regions of perforation and whose effective properties are estimated from the solution of the appropriate local problems set on the unit cell of the layer. Our goal is to derive working formulas for the entire complex of the thermoelastic properties of the periodic network. The effective thermoelastic properties of carbon nanotubes were predicted using asymptotic homogenization method. Moreover, in order to verify the results of analytical predictions, a detailed finite element analysis is followed to investigate the thermoelastic response of the unit cells and the entire graphene sheet network.

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Al-Kharusi, Moosa S. M., Tasneem Pervez i Khalid Alz-Zebdeh. "Effect of Chirality and Geometry on the Young’s Modulus of Graphene Structure Using Spring Based Finite Element Approach". W ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-37972.

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The development of nanocomposite materials has led to vast progress in the field of composite materials as well as in finding new solutions to technological problem that have not been solved yet. Among the newly developed materials, the most attracting is the graphene based nanocomposites that has superior mechanical, thermal, optical and electrical properties. The hexagonal structure and the high strength of carbon–carbon bond in graphene yield strong material. Estimation of mechanical properties of the graphene becomes one of the important issues, which should be reasonably and accurately predicted to further promote its application development. Simulation and modeling techniques play a significant role in characterizing mechanical behavior especially for nanomaterials where the experimental measurements are very difficult to conduct. The aim of the current study is to estimate the Young’s modulus of elasticity of single layered graphene sheet using new spring based finite element approach. The use of spring finite elements help to accurately define the interatomic bonded interactions between carbon atoms based on potential energies obtained from molecular dynamics theory. The inclusion of both linear and torsion terms simultaneously has resulted in improved values of the Young’s modulus. The nodes in the finite element model define the position of carbon atoms in the graphene which are connected with appropriate spring-type elements. These elements are used to build the finite element model based on the observation that beam or truss elements require geometrical variables such as area and inertia, which are not required in the case of springs. Each node of this element provides six degrees of freedom (3 translations and 3 rotations) at which the complex interactions presented in the atomistic level can be considered. Parametric study is performed to investigate the effect of chirality and geometric parameters on the Young’s modulus of single graphene layer. The results are in good agreement with the published numerical and experimental results. The obtained results show an isotropic behavior, in contrast to limited molecular dynamic simulations. Young’s modulus of graphene shows a high dependency of stiffness on layer thickness.

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Dayal, Vinay, Gohar M. Mir i David K. Hsu. "Damage Modeling in Honeycomb Panels for Tap Testing". W ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-1627.

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Abstract Effect of damage on Composite Honeycomb panel due to low speed impact is of significance. The result of such impact is damage such as crushing or buckling of the core, core to face de-bonding and local de-lamination of the plies. The damage, however, may be invisible to human eye but can result in significant degradation of stiffness and strength of Honeycomb structure. Of all the NDE techniques available, Tap Test seems to be the cheapest and most suited for the detection of damage in face-sheets, the face-sheet to core de bonding, and core damage. Instrumented Tap Testing with scanning capability makes it a very attractive NDE tool. This work is concerned with modeling the Tap Test on composite honeycomb panels by Finite Elements in both static and dynamic modes. Interactive Finite Element model has been developed having option of creating multiple defects of varying size at desired location within the core material. Model is generated using Graphite/Epoxy quasi-isotropic laminate as face sheet material with Nomex paper core, simulating condition of crushed core. The model was analyzed by applying point load (equivalent force of the impacting projectile) at the node of concern. The defect is modeled as a gap in the core. Samples were made having defects at different core height and were analyzed using Finite Element Methods (ANSYS) and by Tap Testing under same boundary conditions and loading. The sensitivity of FE model and Tap Test to damage location and size has been studied and the results are presented.

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