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    An analytical solution to the elastic-plastic behavior of metal matrix composites under tensile loading

    , Article 29th Congress of the International Council of the Aeronautical Sciences, ICAS 2014 ; 2014 Khosoussi, S ; Mondali, M ; Abedian, A ; Sharif University of Technology
    Abstract
    An analytical approach is proposed for studying the elastic-plastic behavior of short fiber reinforced metal matrix composites under tensile loading. In the proposed method, a micromechanical approach is employed, considering an axi-symmetric unit cell including one fiber and the surrounding matrix. First, the governing equations and the boundary conditions are derived and the elastic solution is obtained based on some shear lag type methods. A plastic deformation is considered for the matrix under each small tensile loading step. Then, applying the successive elastic solutions method, all the plastic strain terms are obtained for the matrix. Thereafter, the elastic-plastic stress transfer... 

    New approach for fatigue life prediction of composite plates using micromechanical bridging model

    , Article Journal of Composite Materials ; Volume 49, Issue 3 , February , 2015 , Pages 309-319 ; 00219983 (ISSN) Adibnazari, S ; Farsadi, M ; Koochi, A ; Khorashadizadeh, S. N ; Sharif University of Technology
    SAGE Publications Ltd  2015
    Abstract
    The use of micromechanical models to study composite material's behavior leads to save time and cost. In this paper, bridging micromechanical models have been used in order to observe the behavior of unidirectional laminate composite under fatigue loading. In order to study the fatigue behavior, stiffness degradation has been studied as well as the strength degradation and a driftnet model has been proposed for each of them. The strength degradation has only been studied for the unidirectional fiber, while the stiffness degradation has been studied for the fibers with different fiber angle. The results are compared with macro-mechanical models and other methods in literature  

    Micromechanical fem modeling of thermal stresses in functionally graded materials

    , Article 26th Congress of International Council of the Aeronautical Sciences 2008, ICAS 2008, Anchorage, AK, 14 September 2008 through 19 September 2008 ; Volume 2 , January , 2008 , Pages 2851-2859 ; 9781605607153 (ISBN) Akbarpour, S ; Motamedian, H. R ; Abedian, A ; Sharif University of Technology
    2008
    Abstract
    The most common use of FG materials is as barrier coating against large thermal gradients. Thermal stresses in FG materials, if not released, may cause structural discontinuities in outer surfaces or even inside the material such as cracks, debonding, etc. In this research work, using Finite element method and micromechanical modeling of FG thermal barrier coatings, stresses under thermal and mechanical loadings of the same and different phases have been investigated. Also, the effect of some parameters such as refinement and offsetting of particles on stresses are studied. As for the loading, thermal cycle and in-phase and out-of-phase thermo-mechanical cyclic loadings are considered. The... 

    Effect of axonal fiber architecture on mechanical heterogeneity of the white matter—a statistical micromechanical model

    , Article Computer Methods in Biomechanics and Biomedical Engineering ; 2021 ; 10255842 (ISSN) Hoursan, H ; Farahmand, F ; Ahmadian, M. T ; Sharif University of Technology
    Taylor and Francis Ltd  2021
    Abstract
    A diffusion tensor imaging (DTI) -based statistical micromechanical model was developed to study the effect of axonal fiber architecture on the inter- and intra-regional mechanical heterogeneity of the white matter. Three characteristic regions within the white matter, i.e., corpus callosum, brain stem, and corona radiata, were studied considering the previous observations of locations of diffuse axonal injury. The embedded element technique was used to create a fiber-reinforced model, where the fiber was characterized by a Holzapfel hyperelastic material model with variable dispersion of axonal orientations. A relationship between the fractional anisotropy and the dispersion parameter of... 

    Incorporating multiscale micromechanical approach into PLSNs with different intercalated morphologies

    , Article Journal of Applied Polymer Science ; Volume 119, Issue 6 , September , 2011 , Pages 3347-3359 ; 00218995 (ISSN) Yazdi, A. Z ; Bagheri, R ; Kazeminezhad, M ; Heidarian, D ; Sharif University of Technology
    2011
    Abstract
    The objective of the present study is to predict Young's modulus of polymer-layered silicate nanocomposites (PLSNs) containing fully intercalated structures. The particular contribution of this article is to consider the changes in structural parameters of different intercalated morphologies in vicinity of each other. These parameters include aspect ratio of intercalated stacks, number of silicate layers per stack, d-spacing between the layers, modulus of the gallery phase, and volume fraction of each intercalated morphology. To do this, the effective particle concept has been employed and combined with the Mori-Tanaka micromechanical model. It has been shown that the simultaneous effects of... 

    A new approach to the elastic–plastic stress transfer analysis of metal matrix composites

    , Article Archive of Applied Mechanics ; Volume 85, Issue 11 , November , 2015 , Pages 1701-1717 ; 09391533 (ISSN) Khosoussi, S ; Mondali, M ; Abedian, A ; Sharif University of Technology
    Springer Verlag  2015
    Abstract
    An analytical approach is proposed for studying the elastic–plastic behavior of short-fiber-reinforced metal matrix composites under tensile loading. In the proposed research, a micromechanical approach is employed, considering an axisymmetric unit cell including one fiber and the surrounding matrix. First, the governing equations and the boundary conditions are derived and the elastic solution is obtained based on some shear-lag-type methods. Since under normal loading conditions and according to the fiber material characteristics, the metal matrix undergoes plastic deformation, while the fiber remains within the elastic region, a plastic deformation is considered for the matrix under each... 

    Characterization of polyamide 6/carbon nanotube composites prepared by melt mixing-effect of matrix molecular weight and structure

    , Article Composites Part B: Engineering ; Volume 78 , 2015 , Pages 50-64 ; 13598368 (ISSN) Faghihi, M ; Shojaei, A ; Bagheri, R ; Sharif University of Technology
    Elsevier Ltd  2015
    Abstract
    Effects of molecular weight and structure of polyamide 6 (PA6) on morphology and properties of PA6/MWCNT prepared by melt mixing were investigated. Microscopic analysis showed fine dispersion of MWCNT within low viscosity PA6s due to domination of melt infiltration into MWCNT agglomerate at low viscosity matrices with linear structure. Rheological data indicated good interfacial interaction with no percolation of MWCNT up to 2 wt% loading. DSC thermograms showed nucleating role of MWCNT on crystallization of PA6s with marginal effect on crystallinity. Experimental data supported with micromechanical model showed limited improvement on mechanical properties, but it was closely consistent with... 

    Rate-dependent behavior of connective tissue through a micromechanics-based hyper viscoelastic model

    , Article International Journal of Engineering Science ; Volume 121 , 2017 , Pages 91-107 ; 00207225 (ISSN) Fallah, A ; Ahmadian, M. T ; Mohammadi Aghdam, M ; Sharif University of Technology
    Abstract
    In this paper, a micromechanical study on rate-dependent behavior of connective tissues is performed. To this end, a hyper viscoelastic constitutive model consisting a hyperelastic part for modeling equilibrium response of tissues and a viscous part using a hereditary integral is proposed to capture the time-dependent behavior of the tissues. With regard to the hierarchical structure of the tissue, strain energy function are developed for modeling elastic response of the tissue constituents i.e. collagen fibers and ground matrix. The rate-dependency is incorporated into the model using a viscous element with rate-dependent relaxation time. The proposed constitutive model is implemented into... 

    Nonlinear mechanics of soft composites: hyperelastic characterization of white matter tissue components

    , Article Biomechanics and Modeling in Mechanobiology ; Volume 19, Issue 3 , 2020 , Pages 1143-1153 Yousefsani, S. A ; Shamloo, A ; Farahmand, F ; Sharif University of Technology
    Springer  2020
    Abstract
    This paper presents a bi-directional closed-form analytical solution, in the framework of nonlinear soft composites mechanics, for top-down hyperelastic characterization of brain white matter tissue components, based on the directional homogenized responses of the tissue in the axial and transverse directions. The white matter is considered as a transversely isotropic neo-Hookean composite made of unidirectional distribution of axonal fibers within the extracellular matrix. First, two homogenization formulations are derived for the homogenized axial and transverse shear moduli of the tissue, based on definition of the strain energy density function. Next, the rule of mixtures and... 

    Effect of axonal fiber architecture on mechanical heterogeneity of the white matter—a statistical micromechanical model

    , Article Computer Methods in Biomechanics and Biomedical Engineering ; Volume 25, Issue 1 , 2022 , Pages 27-39 ; 10255842 (ISSN) Hoursan, H ; Farahmand, F ; Ahmadian, M. T ; Sharif University of Technology
    Taylor and Francis Ltd  2022
    Abstract
    A diffusion tensor imaging (DTI) -based statistical micromechanical model was developed to study the effect of axonal fiber architecture on the inter- and intra-regional mechanical heterogeneity of the white matter. Three characteristic regions within the white matter, i.e., corpus callosum, brain stem, and corona radiata, were studied considering the previous observations of locations of diffuse axonal injury. The embedded element technique was used to create a fiber-reinforced model, where the fiber was characterized by a Holzapfel hyperelastic material model with variable dispersion of axonal orientations. A relationship between the fractional anisotropy and the dispersion parameter of... 

    Piezoelectric composites with periodic multi-coated inhomogeneities

    , Article International Journal of Solids and Structures ; Volume 47, Issue 21 , October , 2010 , Pages 2893-2904 ; 00207683 (ISSN) Hashemi, R ; Weng, G. J ; Kargarnovin, M. H ; Shodja, H. M ; Sharif University of Technology
    Abstract
    A new, robust homogenization scheme for determination of the effective properties of a periodic piezoelectric composite with general multi-coated inhomogeneities is developed. In this scheme the coating does not have to be thin, the shape and orientation of the inclusion and coatings do not have to be identical, their centers do not have to coincide, their properties do not have to remain uniform, and the microstructure can be with the 2D elliptic or the 3D ellipsoidal inclusions. The development starts from the local electromechanical equivalent inclusion principle through the introduction of the position-dependent equivalent eigenstrain and electric field. Then with a Fourier series... 

    A three-dimensional micromechanical model of brain white matter with histology-informed probabilistic distribution of axonal fibers

    , Article Journal of the Mechanical Behavior of Biomedical Materials ; Volume 88 , 2018 , Pages 288-295 ; 17516161 (ISSN) Yousefsani, S. A ; Farahmand, F ; Shamloo, A ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    This paper presents a three-dimensional micromechanical model of brain white matter tissue as a transversely isotropic soft composite described by the generalized Ogden hyperelastic model. The embedded element technique, with corrected stiffness redundancy in large deformations, was used for the embedment of a histology-informed probabilistic distribution of the axonal fibers in the extracellular matrix. The model was linked to a multi-objective, multi-parametric optimization algorithm, using the response surface methodology, for characterization of material properties of the axonal fibers and extracellular matrix in an inverse finite element analysis. The optimum hyperelastic... 

    A three-dimensional statistical volume element for histology informed micromechanical modeling of brain white matter

    , Article Annals of Biomedical Engineering ; Volume 48, Issue 4 , 2020 , Pages 1337-1353 Hoursan, H ; Farahmand, F ; Ahmadian, M. T ; Sharif University of Technology
    Springer  2020
    Abstract
    This study presents a novel statistical volume element (SVE) for micromechanical modeling of the white matter structures, with histology-informed randomized distribution of axonal tracts within the extracellular matrix. The model was constructed based on the probability distribution functions obtained from the results of diffusion tensor imaging as well as the histological observations of scanning electron micrograph, at two structures of white matter susceptible to traumatic brain injury, i.e. corpus callosum and corona radiata. A simplistic representative volume element (RVE) with symmetrical arrangement of fully alligned axonal fibers was also created as a reference for comparison. A...