ORCID Profile
0000-0003-4691-6252
Current Organisation
University of Southampton
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Publisher: Trans Tech Publications, Ltd.
Date: 02-2011
DOI: 10.4028/WWW.SCIENTIFIC.NET/KEM.471-472.606
Abstract: In spite of a vast background on cohesive constitutive law and its use for various analyses such as delamination in composite laminates, some numerical aspects of that have been less explored and reported in the literature. The aim of this paper is to study the phenomenon of spurious stress oscillation and also dominant process zone (where damage has its most significant evolution) in delamination modeling. For this purpose, distribution of normal stress and damage parameter of different DCB specimen are analyzed. Distribution of stress around the process zone indicates spurious oscillation just ahead of the delamination tip where damage parameter is zero and no effect of this phenomenon is seen on results of applied load versus opening displacement. Additionally, it is shown that larger values of penalty stiffness lead in smaller length of dominant process zone and very large values of penalty stiffness pushes the distribution of damage parameter to become step-like function. Authors believe that this effect is in fact the main reason of un-converged solution of models with too large penalty values.
Publisher: Trans Tech Publications, Ltd.
Date: 09-2016
DOI: 10.4028/WWW.SCIENTIFIC.NET/KEM.713.167
Abstract: In this paper, a viscoelastic-damage cohesive zone model is formulated and discussed. The interface element constitutive law has two elastic and damage regimes. Viscoelastic behaviour has been assumed for the shear stress in the elastic regime. Three element Voigt model has been used for the formulation of relaxation modulus of the material. Shear Stress has been evaluated in the elastic regime of the interface with integration over the history of the applied strain at the interface. Damage evolution proceeds according to the bilinear cohesive constitutive law up to the complete decohesion. Numerical ex les for one element model has been presented to see the effect of parameters on cohesive constitutive law.
Publisher: SAGE Publications
Date: 19-09-2012
Abstract: This article is devoted to the modeling of spread kind of damages such as matrix cracking and induced delamination in symmetric and asymmetric cross-ply laminates of composite materials using cohesive elements. For matrix crack modeling, parallel rows of cohesive elements are used between every row of 2D elements in 90° layers. Delamination is also modeled by cohesive elements at the 90°/0° interface. Since matrix cracking is a diffuse kind of damage mechanism, application of cohesive elements is not straightforward, and special techniques are necessary to resolve the modeling difficulties. For this purpose, two techniques of “bisecting” and “random distribution of strength of cohesive elements” are proposed here. Both techniques are applied to various symmetric laminates of [0/90 3 ] s and [90 n /0] s (n = 1 to 3). The predicted stiffness and damage progresses from both techniques are in good agreement with the experimental results. Then, asymmetric cross-ply laminates of [90 n /0] (n = 1 to 3) are analyzed to show the capability of this method in progressive damage analyses. The proposed method is less restricted in comparison with available micromechanical methods and is able to predict damage initiation, propagation and damage-mode transition for any symmetric and asymmetric cross-ply sequence. Therefore, this method can be used for development of “in-plane damage” of constitutive laws especially when specimens are subjected to complex loading and boundary conditions.
Publisher: Elsevier BV
Date: 07-2009
Publisher: Elsevier BV
Date: 07-2018
Publisher: SAGE Publications
Date: 15-10-2015
Abstract: A computational constitutive model is presented to predict matrix cracking evolution in laminates under in-plane loading. Transverse cracks are treated as separate discontinuities in the micro-model that provides damage parameters for the macro-model. Both micro- and macro-models are implemented using finite element analysis, specifically, ANSYS, to avoid limitation of analytical micro-modeling. The computational cost of the micro-model is limited to constructing a database of micro-model predictions a priori. The macro-model is simply a finite element analysis discretization of the structure using plane stress or shell elements in ANSYS. The macro-model queries the database, which effectively becomes a constitutive model. The damage surfaces in the database are obtained from the results of large number of finite element micro-scale (unit-cell) analyses. The proposed procedure is implemented in ANSYS as a usermaterial subroutine for transverse crack initiation and propagation in symmetric cross-ply and [0 r /(θ / −θ) s /0 n ] s laminates under in-plane loads. This method is also examined to study matrix crack evolution in tensile specimen with open hole, and the results found to be in good agreement with available experimental data.
Publisher: Elsevier BV
Date: 06-2013
Publisher: Elsevier BV
Date: 12-2014
Publisher: Elsevier BV
Date: 11-2018
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Meisam Jalalvand.