Search for: micromechanics
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    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
    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  

    Modeling of stiffening and strengthening in nano-layered silicate/epoxy

    , Article International Journal of Engineering, Transactions A: Basics ; Volume 30, Issue 1 , 2017 , Pages 93-100 ; 17281431 (ISSN) Marouf, B. T ; Pearson, R. A ; Bagheri, R ; Sharif University of Technology
    The aim of this paper is to investigate adhesion property between nano-layered filler and the polymer matrix using a combination of experimental and micromechanical models as well as the changes in yield strength and stiffness of a layered silicate-filled epoxy nanocomposite. The results indicate that addition of intercalated layered silicate particles increased Young's modulus and yield strength of the epoxy resin, although the increases in stiffness and yield strength are modest, 30% and 4%, respectively. In addition, experimental results were compared with predictive stiffening and strengthening models. The rule of mixtures provides an upper bound for the modulus in these materials, while... 

    Interacting cracks and ellipsoidal inhomogeneities by the equivalent inclusion method

    , Article Journal of the Mechanics and Physics of Solids ; Volume 51, Issue 5 , 2003 , Pages 945-960 ; 00225096 (ISSN) Shodja, H. M ; Rad, I. Z ; Soheilifard, R ; Sharif University of Technology
    Based on the Eshelby's equivalent inclusion method (EIM) and Hill's theorem on discontinuities of elastic fields across the interfaces, a theory for the determination of the stress intensity factors (SIFs) of arbitrarily oriented interacting cracks under non-uniform far-field applied stress (strain) is developed. As shown in this investigation the EIM proposed by Moschovidis and Mura can be extended for treatment of such problems, but their formulations are quite cumbersome and computationally inefficient. An alternative analytical approach is proposed that is computationally more efficient, and unlike the method of Moschovidis and Mura can easily handle complex problems of interacting... 

    Modeling of Moisture-Induced Damage in Asphalt Mixtures

    , M.Sc. Thesis Sharif University of Technology Bozorgzad, Ashkan (Author) ; Tabatabaee, Nader (Supervisor)
    The deleterious effect of moisture on the structural integrity of asphalt mixtures has been recognized as one of the main causes of early deterioration of asphalt pavements. This phenomenon, usually referred to as moisture damage, is defined as the progressive loss of structural integrity of the mixture. Moisture damage is associated with the development of different physical, mechanical and chemical processes occurring within the microstructure of the mixture at different intensities and rates. Although there have been important advancements in identifying and characterizing this phenomenon, there is still a lack of understanding of the damage mechanisms occurring at the... 

    A Micromechanical Progressive Damage Algorithm for Prediction of Failure in Composite Laminates

    , M.Sc. Thesis Sharif University of Technology Rajaeenezhad, Iman (Author) ; Hosseini Kordkheili, Ali (Supervisor)
    Macro models which are used to predict failure of composite structures in most cases predict ¬reasonable results; however, they are not able to consider micro level parameters such as micro cracks. Furthermore, these failure macro models need various empirical data. Considering micromechanical construction of composites; including fiber, matrix and their interfaces, using micromechanical models for predicting failures in these phases is more appropriate. The aim of this study is to represent a micro-mechanical algorithm in order to predict progressive failures of fiber-reinforced composites. The failure model which is used in this study is a micromechanical modeling of failure (MMF) model,... 

    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
    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... 

    Performing assembly-based method engineering by architecture-centric method engineering approach

    , Article EMS 2008, European Modelling Symposium, 2nd UKSim European Symposium on Computer Modelling and Simulation, Liverpool, 8 September 2008 through 10 September 2008 ; 2008 , Pages 181-186 ; 9780769533254 (ISBN) Ahmadi, H ; Rashidi, H ; Moaven, S ; Habibi, J ; Sharif University of Technology
    Due to the necessity for methods that are able to handle complexities of systems, use of Method Engineering (ME) to construct more adaptable and flexible methods has become of importance. Assemblybased approach is the most well-known approach of ME that performs method construction by reusing and assembling different method fragments. This approach, like other approaches of ME, suffers from the lack of suitable guidelines. In this way, architecture-centric method engineering (ArCME) is a new approach which aims at performing ME processes in a more disciplined and cohesive way. In this paper, process of assemblybased ME is enhanced by ArCME. Furthermore, benefits of implementing the process... 

    A micromechanical study of rolling and sliding contacts in assemblies of oval granules

    , Article International Journal for Numerical and Analytical Methods in Geomechanics ; Volume 27, Issue 5 , 2003 , Pages 403-424 ; 03639061 (ISSN) Shodja, H. M ; Nezami, E. G ; Sharif University of Technology
    The evolution of the microstructure of an assembly of cohesionless granular materials with associated pores, which carry the overall applied stresses through frictional contacts is a complex phenomenon. The macroscopic flow of such materials take place by the virtue of the relative rolling and sliding of the grains on the micro-scale. A new discrete element method for biaxial compression simulations of random assemblies of oval particles with mixed sizes is introduced. During the course of deformation, the new positions of the grains are determined by employing the static equilibrium equations. A key aspect of the method is that, it is formulated for ellipse cross-sectional particles, hence... 

    Optimization of waveform shape and frequency in periodic reverse electroplating

    , Article 12th International Conference on Microelectronics, ICM 2000, 31 October 2000 through 2 November 2000 ; Volume 2000-October , 2000 , Pages 335-339 ; 9643600572 (ISBN) Motieifar, A ; Khorasani, S ; Rashidian, B ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2000
    In this report, the time-dependent carrier concentration in electrolytic cells, due to some basic periodic shapes, has been studied. Exact analytical solutions for step, sinusoidal and periodic pulse reverse inputs are derived. The effect of frequency, forward and reverse amplitudes, and pulse modulation width are investigated. Analytical solution of the model is obtained as a Fourier series, using Laplace transformations applied to a one-dimensional model with linearized Butler-Volmer electrode kinetics. The results are applied to an acid-copper bath and discussed. It is shown that there exist optimal operation points or optimal current waveforms to obtain efficient and enhanced deposition... 

    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
    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... 

    An Investigation on Mechanical and Physical Properties of PP-Short Jute Fibers Composites

    , M.Sc. Thesis Sharif University of Technology Barakchian, Masoud (Author) ; Bagheri, Reza (Supervisor) ; Seyed Reihani, Morteza (Supervisor)
    In recent years, due to greater attention scientific communities to environment and environmental friendly material, use of natural fibers as reinforcing the polymers has increased significantly. High specific strength, low density, cheap, stiffness and recycled by nature, are including promotional items using natural fibers as reinforcing in the polymer composites. In This study has tried in the first place an appropriate method for producing polypropylene composites reinforced with short jute fibers should be presented and then the physical and mechanical properties of composites will be investigated. Used MAPP and Silane for compatibility took improved between natural jute fibers as a... 

    Entanglement and Decoherence in Optomechanical Systems Coupled through Photothermal Effects

    , Ph.D. Dissertation Sharif University of Technology Abdi, Mehdi (Author) ; Bahrampour, Alireza (Supervisor)
    Optomechanical systems have attracted considerable attention in the last decade. Such a raising prominence is mainly due to its capability in providing new insight into the quantum behavior of macroscopic objects and exploring the interface between quantum and classical mechanics. Alongside this fundamental quest, cavity optomechanics has many other benefits, ranging from very precise measurements on forces and positions to quantum information processing. In this thesis, we investigate quantum properties of such systems. Particularly, we study cooling of the mechanical resonator toward its ground state and the entanglement between this mechanical resonator and the cavity field. Cooling the... 

    Composites with superspherical inhomogeneities

    , Article Philosophical Magazine Letters ; Volume 89, Issue 7 , 2009 , Pages 439-451 ; 09500839 (ISSN) Hashemi, R ; Avazmohammadi, R ; Shodja, H. M ; Weng, G. J ; Sharif University of Technology
    In contrast to the traditional study of composites containing ellipsoidal inclusions, we highlight some calculated results for the effective moduli when the inclusion shape can be described by the superspherical equation, [image omitted], such that when p = 2 it reduces to a sphere and when p it becomes a perfect cube. We consider the cases of both aligned and randomly oriented superspherical inclusions with isotropic, cubic, and transversely isotropic properties, and show how the shape parameter, p, affects the overall moduli of the composites during the spherical to cuboidal transition  

    Basic modifications in 3D micromechanical modeling of short fiber composites with bonded and debonded fiber end

    , Article Computational Materials Science ; Volume 40, Issue 3 , 2007 , Pages 421-433 ; 09270256 (ISSN) Abedian, A ; Mondali, M ; Pahlavanpour, M ; Sharif University of Technology
    A modified analytical model is developed for analysis of 3D elastic stress fields in short fiber composites subjected to an applied axial load. Two sets of exact displacement solutions for the matrix and fiber are derived based on the theory of elasticity. The superposition state of these solutions are then used to obtain the analytical expressions for the 3D stress field components over the entire composite system including the fiber end region, which is modeled by the use of imaginary fiber technique. The main difference with the previous works here is that the stress field is considered to be a function of both radial and axial directions. Such an assumption made it possible to calculate... 

    Simulation of fiber/matrix debonding in unidirectional composites under fatigue loading

    , Article Journal of Reinforced Plastics and Composites ; Volume 26, Issue 8 , 2007 , Pages 743-760 ; 07316844 (ISSN) Zabihpoor, M ; Adibnazari, S ; Sharif University of Technology
    The efficiency of fiber/matrix interface bonding in composites has an important influence on their overall performance. This article deals with the simulation of interface imperfection effect as it grows under fatigue loading. The relations have been derived based on the constituents' properties for the primary damage mode in unidirectional composites and boundary conditions defined for elements of the micromechanics model. Conformation of model stiffness predictions with the best described residual stiffness model indicates the way to find the remaining constants in the simulated relation. Finally through this relation, cyclic corrected stress components in constituents could be determined.... 

    A micromechanics approach for fatigue of unidirectional fibrous composites

    , Article Iranian Polymer Journal (English Edition) ; Volume 16, Issue 4 , 2007 , Pages 219-232 ; 10261265 (ISSN) Zabihpoor, M ; Adibnazari, S ; Sharif University of Technology
    The overall mechanical properties of composite materials are dependent on the mechanical response of individual constituents and their interactions while they may be relatively easy to determine. This paper represents a simulation process by which the cyclic stresses and fatigue loadings on its constituents could be predicted for an under fatigue loading lamina. Hence, the unidirectional composites fatigue would be studied through its constituents. The proposed model introduces a new coupled stiffness/strength technique by relating lamina stiffness to the stress field in its constituents. Therefore, the stress field and strength considerations in its constituents could be studied when the... 

    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
    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... 

    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
    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... 

    Micromechanics and constitutive modeling of connective soft tissues

    , Article Journal of the Mechanical Behavior of Biomedical Materials ; Volume 60 , 2016 , Pages 157-176 ; 17516161 (ISSN) Fallah, A ; Ahmadian, M. T ; Firozbakhsh, K ; Aghdam, M. M ; Sharif University of Technology
    Elsevier Ltd 
    In this paper, a micromechanical model for connective soft tissues based on the available histological evidences is developed. The proposed model constituents i.e. collagen fibers and ground matrix are considered as hyperelastic materials. The matrix material is assumed to be isotropic Neo-Hookean while the collagen fibers are considered to be transversely isotropic hyperelastic. In order to take into account the effects of tissue structure in lower scales on the macroscopic behavior of tissue, a strain energy density function (SEDF) is developed for collagen fibers based on tissue hierarchical structure. Macroscopic response and properties of tissue are obtained using the numerical... 

    Micromechanical Modeling the Viscoelastic Performance of the Asphalt Concrete with Finite Element

    , M.Sc. Thesis Sharif University of Technology Mohammad Karimi, Mohammad (Author) ; Tabatabaee, Nader (Supervisor)
    Asphalt concrete is a composite mixture of three phases; aggregate, bitumen and air void. Stress and strain distributions obtained from macroscopic modeling yield different results due to distinctly different mechanical properties of the above-mentioned phases. In this study a more exact analysis of the stress and strain, were carried out by considering the mixture as a two-phase composite; aggregate and mastic phases. Asphalt concrete was considered a composite material consisted of sand mastic and aggregate. Aggregate and mastic phases were separated and response of the loaded asphalt mixture was investigated. Aggregates finer than 2.36 mm in diameter, filler and bitumen consist the...