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  • Open Access

    ARTICLE

    Design of Aligned Carbon Nanotubes Structures Using Structural Mechanics Modeling
    Part 2: Aligned Carbon Nanotubes Structure Modeling

    J. Joseph1, Y. C. Lu1

    CMC-Computers, Materials & Continua, Vol.37, No.1, pp. 59-75, 2013, DOI:10.3970/cmc.2013.037.059

    Abstract The aligned carbon nanotube (A-CNT) structure is composed of arrays of individual CNTs grown vertically on a flat substrate. The overall structure and properties of an A-CNTs are highly dependent upon the designs of various architectures and geometric parameters. In Part 2, we have presented the detailed designs and modeling of various aligned carbon nanotube structures. It is found the A-CNT structures generally have much lower modulus than an individual CNT. The reason is due to the high porosity and low density of the A-CNT structures, since the interstitial space between nanotubes is mostly occupied by air. Increasing the nanotube… More >

  • Open Access

    ARTICLE

    Design of Aligned Carbon Nanotubes Structures Using Structural Mechanics Modeling
    Part 1: Theory and Individual Carbon Nanotube Modeling

    J. Joseph1, Y. C. Lu1

    CMC-Computers, Materials & Continua, Vol.37, No.1, pp. 39-57, 2013, DOI:10.3970/cmc.2013.037.039

    Abstract Aligned carbon nanotubes structures are emerging new materials that have demonstrated superior mechanical, thermal, and electrical properties and have the huge potential for a wide range of applications. In contrast with traditional materials whose microstructures are relatively "fixed", the aligned carbon nanotube materials have highly "tunable" structures. Therefore, it is crucial to have a rational strategy to design and evaluate the architectures and geometric factors to help process the optimal nanotube materials. Astructural mechanics based computational modeling is used for designing the aligned carbon nanotubes structures. Part 1 of the papers presents the theory of the computational method as well… More >

  • Open Access

    ARTICLE

    Problems of Micromorphic Elastic Bodies Approached by Lagrange Identity Method

    M. Marin1, S. R. Mahmoud2,3, K. S. Al-Basyouni4

    CMC-Computers, Materials & Continua, Vol.37, No.1, pp. 23-37, 2013, DOI:10.3970/cmc.2013.037.023

    Abstract Taking advantage of the flexibility of Lagrange’s identity, we prove the uniqueness theorem and some continuous dependence theorems without recourse to any energy conservation law, or to any boundedness assumptions on the constitutive coefficients. Also, we avoid the use of positive definiteness assumptions on the constitutive coefficients, even if these results are related to the difficult mixed problem in elasticity of micromorphic bodies. More >

  • Open Access

    ARTICLE

    Stochastic Macro Material Properties, Through Direct Stochastic Modeling of Heterogeneous Microstructures with Randomness of Constituent Properties and Topologies, by Using Trefftz Computational Grains (TCG)

    Leiting Dong1,2, Salah H. Gamal3, Satya N. Atluri2,4

    CMC-Computers, Materials & Continua, Vol.37, No.1, pp. 1-21, 2013, DOI:10.3970/cmc.2013.037.001

    Abstract In this paper, a simple and reliable procedure of stochastic computation is combined with the highly accurate and efficient Trefftz Computational Grains (TCG), for a direct numerical simulation (DNS) of heterogeneous materials with microscopic randomness. Material properties of each material phase, and geometrical properties such as particles sizes and distribution, are considered to be stochastic with either a uniform or normal probabilistic distributions. The objective here is to determine how this microscopic randomness propagates to the macroscopic scale, and affects the stochastic characteristics of macroscopic material properties. Four steps are included in this procedure: (1) using the Latin hypercube sampling,… More >

  • Open Access

    ARTICLE

    A Cell Method Stress Analysis in Thin Floor Tiles Subjected to Temperature Variation

    E. Ferretti1

    CMC-Computers, Materials & Continua, Vol.36, No.3, pp. 293-322, 2013, DOI:10.3970/cmc.2013.036.293

    Abstract The Cell Method is applied in order to model the debonding mechanism in ceramic floor tiles subjected to positive thermal variation. The causes of thermal debonding, very usual in radiant heat floors, have not been fully clarified at the moment. There exist only a few simplified analytical approaches that assimilate this problem to an eccentric tile compression, but these approaches introduce axial forces that, in reality, do not exist. In our work we have abandoned the simplified closed form solution in favor of a numerical solution, which models the interaction between tiles and sub-base more realistically, when the positive thermal… More >

  • Open Access

    ARTICLE

    Theoretical Modeling of the Radiative Properties and Effective Thermal Conductivity of the Opacified Silica Aerogel

    Zichun Yang1,2,3, Gaohui Su1,4, Fengrui Sun1

    CMC-Computers, Materials & Continua, Vol.36, No.3, pp. 271-292, 2013, DOI:10.3970/cmc.2013.036.271

    Abstract In this paper, we investigate the radiative properties and the effective thermal conductivity (ETC) of the opacified silica aerogel by theoretical method. The radiative properties of the opacified silica aerogel are obtained by the modified Mie Scattering Theory that is used for particle scattering in absorbing medium. The modified gamma distribution is used to take account of the non-uniformity of the particle size. The solid thermal conductivity of the composite material is obtained by considering the scale effect of the particles. Based on these calculated thermophysical properties the coupled heat conduction and radiation through the evacuated opacified aerogel are solved… More >

  • Open Access

    ARTICLE

    Numerical Evaluation of Variation in ‘Characteristic Distance’ due to Fracture Specimen Thickness and Temperature

    Sanjeev Saxena1, Raghvendra Singh2, Geeta Agnihotri2

    CMC-Computers, Materials & Continua, Vol.36, No.3, pp. 257-270, 2013, DOI:10.3970/cmc.2013.036.257

    Abstract The present numerical study is an attempt to understand the dependency of characteristic distance on the fracture specimen thickness and temperature. The presented work will be useful to establish the characteristic distance prediction methodology using three dimensional FEM model. Based on the methods proposed for the numerical prediction of characteristic distance, it comes out that it depends on fracture specimen thickness and finally it converges after a specified thickness of fracture specimen. In Armco iron material, characteristic distance varies in temperature ranges where dynamic strain ageing phenomenon is observed, initially decrease and then increases again. More >

  • Open Access

    ARTICLE

    Effect of the Strain Rate and Microstructure on Damage Growth in Aluminum

    R. R. Valisetty1, A.M. Dongare2, A.M. Rajendran3, R. R. Namburu1

    CMC-Computers, Materials & Continua, Vol.36, No.3, pp. 231-255, 2013, DOI:10.3970/cmc.2013.036.231

    Abstract Materials used in soldier protective structures, such as armor, vehicles and civil infrastructures, are being improved for performance in extreme dynamic environments. Nanocrystalline metals show significant promise in the design of these structures with superior strengths attributed to the dislocation-based and grain-boundary-based processes as compared to their polycrystalline counterparts. An optimization of these materials, however, requires a fundamental understanding of damage evolution at the atomic level. Accordingly, atomistic molecular dynamics simulations are performed using an embedded-atom method (EAM) potential on three nano-crystalline aluminum atom systems, one a Voronoi-based nano-crystalline system with an average grain size of 10 nm, and the… More >

  • Open Access

    ARTICLE

    Thermal-Mechanical and Thermodynamic Properties of Graphene Sheets using a Modified Nosé-Hoover Thermostat

    Ching-Feng Yu1, Wen-Hwa Chen1,2, Kun-Ling Chen1, Hsien-Chie Cheng2,3

    CMC-Computers, Materials & Continua, Vol.36, No.2, pp. 203-229, 2013, DOI:10.3970/cmc.2013.036.203

    Abstract The investigation assesses the thermal-mechanical and thermodynamic properties of various graphene sheets using a modified Nosé-Hoover (NH) thermostat method incorporated with molecular dynamics (MD) simulation. The investigation begins with an exploration of their thermal-mechanical properties at atmospheric pressure, including Young’s modulus, shear modulus, Poisson’s ratio, specific heats and linear and volumetric coefficients of thermal expansion (CTE). Two definitions of the line change ratio (ΔL/L) are utilized to determine the linear CTE of graphene sheets, and the calculations are compared with each other and data in the literature. To estimate the volumetric CTE values, the Connolly surface method is applied to… More >

  • Open Access

    ARTICLE

    Heat Conduction Analysis of Nonhomogeneous Functionally Graded Three-Layer Media

    Chien-Ching Ma1,2, Yi-Tzu Chen2

    CMC-Computers, Materials & Continua, Vol.36, No.2, pp. 177-201, 2013, DOI:10.3970/cmc.2013.036.177

    Abstract Functionally graded material (FGM) is a particulate composite with continuously changing its thermal and mechanical properties in order to raise the bonding strength in the discrete composite made from different phases of material constituents. Furthermore, FGM is a potent tool to create an intermediate layer in metal–ceramic composites to avoid the properties discontinuities and reduce, thereby, the residual stresses. For the nonhomogeneous problem, the mathematical derivation is much complicated than the homogeneous case since the material properties vary with coordinate. To analyze the problem, the Fourier transform is applied and the general solution in transform domain is obtained. The inverse… More >

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