The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Ali Ghavami - One of the best experts on this subject based on the ideXlab platform.
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a new analytical Shear Lag based model for prediction of the steady state creep deformations of some short fiber composites
Materials & Design, 2009Co-Authors: Mehdi Mondali, A. Abedian, Ali GhavamiAbstract:A new analytical model based on the Shear-Lag Theory is developed for stress analysis and prediction of the steady state creep deformation of short fiber composites subjected to an applied axial load. A perfect fiber/matrix interface is assumed and the steady state creep behavior of the matrix is described by an exponential law. The results obtained from the proposed analytical solution satisfy the equilibrium and constitutive creep equations. These analytical results are then validated by the FEM modeling. Interestingly, good agreements are found between the analytical and numerical predictions for all the stress and displacement rate components.
Mehdi Mondali - One of the best experts on this subject based on the ideXlab platform.
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Non-linear creep modeling of short-fiber composites using Hermite polynomials, hyperbolic trigonometric functions and power series
Comptes Rendus Mécanique, 2013Co-Authors: Mehdi Mondali, Vahid Monfared, A. AbedianAbstract:Abstract A novel analytical model is presented for analyzing the steady-state creep in short-fiber composites under axial load utilizing the previous Shear-Lag Theory, the imaginary fiber technique and also new approaches of Hermite polynomials, hyperbolic trigonometric functions and power series. The steady-state creep behavior of the matrix is described by an exponential law, while the fibers behave elastically. In this model, in spite of the previous researches, some unknowns such as Shear stress, displacement rates, and creep strain rates are correctly determined in all regions of the unit cell without using any further assumptions. In comparison with previous analytical approaches, the results of the present work are closer to the FEM simulations. This strong method can be used in various problems in applied physics and mechanics such as elastic and plastic analysis of nano-composites.
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Steady state creep behavior of short fiber composites by mapping, logarithmic functions (MF) and dimensionless parameter (DP) techniques
Archives of Civil and Mechanical Engineering, 2012Co-Authors: Vahid Monfared, Mehdi Mondali, A. AbedianAbstract:Abstract A new mathematical insight based on logarithmic, polynomial mapping functions (MF), and dimensionless parameter (DP) models is presented for determination of some unknowns in the steady state creep stage of short fiber composites subjected to axial loading. These unknowns are displacement rate in outer surface of the unit cell, Shear and equivalent stresses at interface and outer surface of the unit cell, and average axial stress in fiber. Dimensionless parameter technique is presented for determination of displacement rate and equivalent stress in outer surface of the unit cell. However, the polynomial mapping function is presented for determination of average axial stress in fiber. Most important novelty of the present research work is determination of the mentioned unknowns in steady state creep by DP and MF techniques without using the Shear-Lag Theory unlike the previous researches. Good agreements are found among the new approaches and previous analytical results based on the Shear-Lag Theory and also numerical solutions (FEM) for predicting the steady state creep behavior in short fiber composites.
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a new analytical Shear Lag based model for prediction of the steady state creep deformations of some short fiber composites
Materials & Design, 2009Co-Authors: Mehdi Mondali, A. Abedian, Ali GhavamiAbstract:A new analytical model based on the Shear-Lag Theory is developed for stress analysis and prediction of the steady state creep deformation of short fiber composites subjected to an applied axial load. A perfect fiber/matrix interface is assumed and the steady state creep behavior of the matrix is described by an exponential law. The results obtained from the proposed analytical solution satisfy the equilibrium and constitutive creep equations. These analytical results are then validated by the FEM modeling. Interestingly, good agreements are found between the analytical and numerical predictions for all the stress and displacement rate components.
A. Abedian - One of the best experts on this subject based on the ideXlab platform.
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Non-linear creep modeling of short-fiber composites using Hermite polynomials, hyperbolic trigonometric functions and power series
Comptes Rendus Mécanique, 2013Co-Authors: Mehdi Mondali, Vahid Monfared, A. AbedianAbstract:Abstract A novel analytical model is presented for analyzing the steady-state creep in short-fiber composites under axial load utilizing the previous Shear-Lag Theory, the imaginary fiber technique and also new approaches of Hermite polynomials, hyperbolic trigonometric functions and power series. The steady-state creep behavior of the matrix is described by an exponential law, while the fibers behave elastically. In this model, in spite of the previous researches, some unknowns such as Shear stress, displacement rates, and creep strain rates are correctly determined in all regions of the unit cell without using any further assumptions. In comparison with previous analytical approaches, the results of the present work are closer to the FEM simulations. This strong method can be used in various problems in applied physics and mechanics such as elastic and plastic analysis of nano-composites.
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Steady state creep behavior of short fiber composites by mapping, logarithmic functions (MF) and dimensionless parameter (DP) techniques
Archives of Civil and Mechanical Engineering, 2012Co-Authors: Vahid Monfared, Mehdi Mondali, A. AbedianAbstract:Abstract A new mathematical insight based on logarithmic, polynomial mapping functions (MF), and dimensionless parameter (DP) models is presented for determination of some unknowns in the steady state creep stage of short fiber composites subjected to axial loading. These unknowns are displacement rate in outer surface of the unit cell, Shear and equivalent stresses at interface and outer surface of the unit cell, and average axial stress in fiber. Dimensionless parameter technique is presented for determination of displacement rate and equivalent stress in outer surface of the unit cell. However, the polynomial mapping function is presented for determination of average axial stress in fiber. Most important novelty of the present research work is determination of the mentioned unknowns in steady state creep by DP and MF techniques without using the Shear-Lag Theory unlike the previous researches. Good agreements are found among the new approaches and previous analytical results based on the Shear-Lag Theory and also numerical solutions (FEM) for predicting the steady state creep behavior in short fiber composites.
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a new analytical Shear Lag based model for prediction of the steady state creep deformations of some short fiber composites
Materials & Design, 2009Co-Authors: Mehdi Mondali, A. Abedian, Ali GhavamiAbstract:A new analytical model based on the Shear-Lag Theory is developed for stress analysis and prediction of the steady state creep deformation of short fiber composites subjected to an applied axial load. A perfect fiber/matrix interface is assumed and the steady state creep behavior of the matrix is described by an exponential law. The results obtained from the proposed analytical solution satisfy the equilibrium and constitutive creep equations. These analytical results are then validated by the FEM modeling. Interestingly, good agreements are found between the analytical and numerical predictions for all the stress and displacement rate components.
Robert M. Mcmeeking - One of the best experts on this subject based on the ideXlab platform.
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Stress concentrations in composites with interface sliding, matrix stiffness and uneven fiber spacing using Shear Lag Theory
International Journal of Solids and Structures, 1999Co-Authors: Chad M. Landis, Robert M. McmeekingAbstract:The stress concentrations near a single fiber break in a unidirectionally reinforced fiber composite are investigated using a Shear Lag Theory within the framework of finite elements. A model for uniformly spaced, well bonded fibers embedded in a matrix that cannot carry axial loads that was formulated previously is first introduced. The solution of this problem involves Fourier transforms and requires only a two-dimensional numerical integration. The work described in the current paper characterizes the stress concentrations around a single fiber break in the presence of fiber/matrix interface sliding, axial matrix stiffness and uneven fiber spacing. Due to the introduction of these complicating factors, the model no longer lends itself to the simple Fourier transformation solution method. For the case of interface sliding a new method is developed to handle sliding in any Shear Lag system. For the cases of axial matrix stiffness and uneven fiber spacing a finite element code specifically written for this problem is used to determine the fiber stresses. The results are discussed in the context of global versus local load sharing, and the effects on composite failure.
Lokeswarappa R. Dharani - One of the best experts on this subject based on the ideXlab platform.
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On matrix splitting in edge notched unidirectional composites
Advanced Composite Materials, 1993Co-Authors: V. G. Mukunda, Lokeswarappa R. DharaniAbstract:An analytical micromechanics model, using consistent Shear Lag Theory is developed to study the splitting mechanism in the edge notched unidirectional composites. The derived expressions include the load carrying capacity of the matrix. The governing differential equations reduce to an eigenvalue problem and thus are solved numerically. The propagation of the split can be predicted in terms of microstructural properties of the constituents for the damage configuration. The analytical results compare favorably with experimental results and model proposed by Tirosh. They also show that there is a region of intense stress concentration at the tip of the split.
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Micromechanical Modeling of Failure in Fiber Reinforced Intermetallic Matrix Composites
International Journal of Damage Mechanics, 1992Co-Authors: Lokeswarappa R. Dharani, Y. Zhao, L. ChaiAbstract:Various failure modes observed in fiber reinforced intermetallic matrix composites are analyzed by using a micromechanical analytical model based on the con sistent Shear Lag Theory. Stress distribution is examined for a number of damage configura tions such as interface split, fiber bridging and secondary cracking. Based on the point stress failure criterion, prediction of failure mode is made for a fiber reinforced unidirec tional composite with central transverse crack and subjected to a remote uniform stress.
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Interfacial Shear stress in SiC fibre-reinforced cordierite
Journal of Materials Science, 1991Co-Authors: Lokeswarappa R. Dharani, Mohamed N. Rahaman, S. H. WangAbstract:An analytical model based on a consistent Shear-Lag Theory was developed to predict the interfacial Shear stress in single fibre pull-out tests. The calculations show that the stress is highly dependent on the specimen thickness and the method of testing. Data for the debond stress and the interfacial Shear stress were measured for single SiC fibres embedded in a magnesium aluminium silicate (cordierite) matrix. The effect of fibre embedded length, processing schedule, and matrix toughening were investigated. For a fixed sample support configuration during testing, good agreement was obtained between the model predictions and experimental data.
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Analysis of Elastic Crack Bridging in Ceramic Matrix Composites
Theoretical and Applied Fracture Mechanics, 1991Co-Authors: Li Chai, Lokeswarappa R. DharaniAbstract:Abstract A micromechanics analytical model based on the consistent Shear Lag Theory is developed for predicting the failure modes in fiber reinforced unidirectional stiff matrix composites. The model accounts for a relatively large matrix stiffness and hence its load carrying capacity. The fiber and matrix stresses are established as functions of the applied stress, crack geometry, and the microstructural properties of the constituents. From the predicted stresses, the mode of failure is established based on a point stress failure criterion. The role of the microstructural parameters of the constituents on the failure modes such as self-similar continuous cracking, crack bridging and debonding parallel to the fibers is assessed.