SANA KOUBAA - Academia.edu (original) (raw)

Papers by SANA KOUBAA

Research paper thumbnail of Application of Factorial Design to Study the Effect of Recycling of HDPE on Rheological and Mechanical Properties

In the plastic industry, scrap is common and can reach important amounts in some applications. Fo... more In the plastic industry, scrap is common and can reach important amounts in some applications. For that reason, reprocessing in the format of mechanical recycling is pretty common among plastic industry for its simplicity and efficiency. However, the stated type of reprocessing causes the degradation of the proprieties of plastic. Hence, recycled plastic is mixed with virgin one. The objective of this work is the investigation of the effect of the variation of the fraction of the recycled plastic (X1) in virgin/recycled blends and number of recycled cycles (X2) using factorial design for HDPE. To attend this objective, two sets of specimens were injected according to 22 factorial design. Mechanical and rheological proprieties were characterized in terms of melt flow index, Vicat softening temperature, elastic tensile strength at 5% (\( \sigma_{\varvec{e}} \)) and tensile strength at yield (\( \sigma_{\varvec{m}} \)). Using nemrodw software, effects plots were plotted. It was depicte...

Research paper thumbnail of Numerical Investigation of Reverse Redrawing Process Using a Non Associated Flow Rule

Deep drawing process is commonly used to produce particular components like aerospace and automot... more Deep drawing process is commonly used to produce particular components like aerospace and automotive structural parts. Based on the drawing ratio, it can be performed in a single or a multiple-stage drawing. Due the complexity of this process, finite element simulations are considered as a powerful tool for the both reasons: reducing times and costs, and improving quality and productivity. The current study is conducted to evaluate the performance and the capability of a non associated flow rule (NAFR) approach on numerical results during reverse re-drawing process of DDQ mild steel metal. The adopted model is implemented on ABAQUS software using user interface material subroutine (VUMAT).

Research paper thumbnail of Reliability based design optimization of coupled acoustic-structure system using generalized polynomial chaos

International Journal of Mechanical Sciences

Abstract In this work, an analytical formulation and numerical implementation of the response of ... more Abstract In this work, an analytical formulation and numerical implementation of the response of the coupled structure-acoustic system were performed. The acoustic pressure inside the cavity as well as the plate displacement are analyzed. This study is combined with a probabilistic analysis to account for variability of different parameters, considered as random variables, which are material properties. A reliability based design optimization (RBDO) using the generalized polynomial chaos (gPC) is addressed. In order to reduce the computational cost of the classical approach of RBDO problem, the optimum safety factor (OSF) method coupled with the gPC procedure is applied to the coupled acoustic-structure systems. Numerical examples showed the effectiveness and efficiency of the OSF based on gPC for the reliability optimization of the structural-acoustic system with probabilistic random variables.

Research paper thumbnail of Experimental and numerical investigation of flexible bulging process of aluminum AA1050-H14 sheet metal with soft tools

The International Journal of Advanced Manufacturing Technology

Research paper thumbnail of Numerical modeling of uncertainty in acoustic propagation via generalized polynomial chaos

Journal of Theoretical and Applied Mechanics

This work aims at increasing the performance prediction for acoustic propagation systems that wil... more This work aims at increasing the performance prediction for acoustic propagation systems that will operate in the presence of the inevitable parameters uncertainty. In the present contribution, the finite element method is applied to solve an acoustic problem described by the Helmholz equation when the geometric and material properties present uncertainty. The influence of the uncertainty of physical parameters on the pressure field is discussed. The results using the polynomial chaos expansion method are compared with Monte Carlo simulations. It is show that uncertainty levels in the input data could result in large variability in the calculated pressure field in the domain.

Research paper thumbnail of Numerical investigation of the forming capability of bulge process by using rubber as a forming medium

The International Journal of Advanced Manufacturing Technology

A finite element simulation of flexible bulge forming of aluminum sheet metal is carried out. The... more A finite element simulation of flexible bulge forming of aluminum sheet metal is carried out. The effect of rubber pad on forming capability is studied by comparing flexible bulge to hydroforming. Based on the theory of Continuum Damage Mechanics (CDM), a local approach with fully coupling between ductile damage and an anisotropic elasto-plastic model with mixed nonlinear kinematic/isotropic hardening is introduced. The model is implemented into a user-defined material (VUMAT) subroutine for the commercial finite element code ABAQUS/Explicit. A Mooney-Rivlin theory is adopted for rubber material behavior. Comparisons between both processes in terms of thickness variation, damage occurrence, and sheet formability are conducted for different rubber shores and friction. Numerical findings are in a good correlation with experiments from literature.

Research paper thumbnail of Investigation of capillary impregnation for permeability prediction of fibrous reinforcements

Journal of Composite Materials, 2015

In thermoplastic pultrusion process, unidirectional glass fibre bundles are very often used as re... more In thermoplastic pultrusion process, unidirectional glass fibre bundles are very often used as reinforcement. This study was motivated by the industrial requirement to evolve from low viscosity thermoset resin processes to high viscosity thermoplastic polymers. The key parameters to control the impregnation process are the permeability of the fibrous reinforcement and the capillary pressure. The current study's objectives are threefold: (1) study the fibres arrangement by X-ray tomography, (2) determine the longitudinal and transversal permeabilities as well as capillary pressure to use them as input parameters of impregnation process in pultrusion and (3) carry out sensitivity analyses of the permeability measurements to the perturbation of fibre structure. To reach these purposes, two theoretical models were used to determine both axial and transversal tow permeability. The axial impregnation of aligned fibres was described by Washburn equation applied to 1D infiltration into ...

Research paper thumbnail of Thermoplastic pultrusion process: Modeling and optimal conditions for fibers impregnation

Journal of Reinforced Plastics and Composites, 2013

ABSTRACT Pultrusion is a crucial method for continuous production of fiber-reinforced composites.... more ABSTRACT Pultrusion is a crucial method for continuous production of fiber-reinforced composites. It was developed several years ago for thermosetting polymer matrices, but the challenge is now to extend it to thermoplastic matrices, with a much higher viscosity. In this paper, we propose an analysis of the parameters influencing fiber impregnation in the conditions of this process. A semi-analytical one-dimensional axisymmetric model based on Darcy’s law and Stokes equations is developed to predict the impregnation profile inside the fibrous phase in the case of a natural impregnation governed by capillary forces. Thanks to a dimensional analysis, it enables to quantify the influence of all the material and testing parameters under the assumption of a slow variation of the geometry of the impregnation die. The cases of a straight and conical dies are discussed. For the first case, an exhaustive numerical study enables to define the optimal processing conditions for a perfect impregnation. Those results are shown to be useful tools for finding an optimal pulling velocity and die length for a given fluid/fibers pair. For the second case, we show that section reductions do not improve impregnation.

Research paper thumbnail of Simple modelling of impregnation in pultrusion process of thermoplastic composites

ABSTRACT Pultrusion is a continuous process with application in the manufacture of fibre-reinforc... more ABSTRACT Pultrusion is a continuous process with application in the manufacture of fibre-reinforced composites. This work reports the impregnation process which is one of the major concerns in pultrusion. We set out to develop a model that describes the flow advancement for a thermoplastic matrix when the reinforcements pass through the die. Therefore, the influence of several processing conditions on the impregnation state has been assessed. An analytical model based upon the Darcy's law and Stokes equation was applied to describe the progression of the radial flow front through porous medium. In this investigation, a unidirectional fibrous medium is adopted and the injected fluid is considered to be Newtonian and incompressible. Results show that the geometry of the die, pulling velocity and obviously the fibres permeability are the major factors influencing the degree of wetting. This analytical methodology is a useful tool to control the matrix impregnation.

Research paper thumbnail of Finite-element analysis of errors on stress and strain measurements in dynamic tensile testing of low-ductile materials

Computers & Structures, 2010

Tensile dynamic tests are essential experiments to develop and validate constitutive equations. I... more Tensile dynamic tests are essential experiments to develop and validate constitutive equations. In this paper, we studied the errors on stress and strain measurement in dynamic tensile tests by using finite-element analysis. Two strain and one stress measures were ...

Research paper thumbnail of Etude analytique et expérimentale de l'imprégnation de composites à matrice thermoplastique dans le procédé de pultrusion

L'une des préoccupations majeures dans la production de profilés composites à matrice thermoplast... more L'une des préoccupations majeures dans la production de profilés composites à matrice thermoplastique par le procédé de pultrusion est de réussir l'imprégnation de la résine thermoplastique par le réseau de fibres de renfort, tout en réalisant une forme correcte et en conservant une excellente résistance aux chocs. En effet, l'imprégnation est un processus difficile en raison de la viscosité élevée des thermoplastiques à l'état fondu. Une étude analytique et expérimentale de l'état de l'imprégnation a été menée. Celle-ci permet de prévoir notamment la perméabilité et la pression capillaire mise en jeu lors de la progression capillaire. Les propriétés du renfort et la distribution des fibres sont mises en évidence notamment grâce à la microtomographie X.

Research paper thumbnail of Numerical study of anisotropic behavior of Aluminum alloy subjected to dynamic perforation

International Journal of Impact Engineering

Abstract A numerical investigation was carried out to analyze in details the perforation process ... more Abstract A numerical investigation was carried out to analyze in details the perforation process of target AA5754-O Aluminum plate when subjected to normal impact at low (up to 25 ms − 1 ) and moderate velocities (ranged between 25 − 50 ms − 1 ). A fully coupled elasto-visco-plastic-damage model is implemented into a user-defined material (VUMAT) subroutine for the commercial finite element code ABAQUS/Explicit. The strain rate effect is considered. Comparison between isotropic J 2 and orthotropic Hill yield criteria associated with isotropic and mixed non-linear isotropic/kinematic hardening was conducted. A parametric study of the effect of anisotropy, plate thickness and impactor nose shapes on ballistic limit and petal forming is carried out. A good agreement is found between numerical and experimental results conducted by other researchers.

Research paper thumbnail of Application of Factorial Design to Study the Effect of Recycling of HDPE on Rheological and Mechanical Properties

In the plastic industry, scrap is common and can reach important amounts in some applications. Fo... more In the plastic industry, scrap is common and can reach important amounts in some applications. For that reason, reprocessing in the format of mechanical recycling is pretty common among plastic industry for its simplicity and efficiency. However, the stated type of reprocessing causes the degradation of the proprieties of plastic. Hence, recycled plastic is mixed with virgin one. The objective of this work is the investigation of the effect of the variation of the fraction of the recycled plastic (X1) in virgin/recycled blends and number of recycled cycles (X2) using factorial design for HDPE. To attend this objective, two sets of specimens were injected according to 22 factorial design. Mechanical and rheological proprieties were characterized in terms of melt flow index, Vicat softening temperature, elastic tensile strength at 5% (\( \sigma_{\varvec{e}} \)) and tensile strength at yield (\( \sigma_{\varvec{m}} \)). Using nemrodw software, effects plots were plotted. It was depicte...

Research paper thumbnail of Numerical Investigation of Reverse Redrawing Process Using a Non Associated Flow Rule

Deep drawing process is commonly used to produce particular components like aerospace and automot... more Deep drawing process is commonly used to produce particular components like aerospace and automotive structural parts. Based on the drawing ratio, it can be performed in a single or a multiple-stage drawing. Due the complexity of this process, finite element simulations are considered as a powerful tool for the both reasons: reducing times and costs, and improving quality and productivity. The current study is conducted to evaluate the performance and the capability of a non associated flow rule (NAFR) approach on numerical results during reverse re-drawing process of DDQ mild steel metal. The adopted model is implemented on ABAQUS software using user interface material subroutine (VUMAT).

Research paper thumbnail of Reliability based design optimization of coupled acoustic-structure system using generalized polynomial chaos

International Journal of Mechanical Sciences

Abstract In this work, an analytical formulation and numerical implementation of the response of ... more Abstract In this work, an analytical formulation and numerical implementation of the response of the coupled structure-acoustic system were performed. The acoustic pressure inside the cavity as well as the plate displacement are analyzed. This study is combined with a probabilistic analysis to account for variability of different parameters, considered as random variables, which are material properties. A reliability based design optimization (RBDO) using the generalized polynomial chaos (gPC) is addressed. In order to reduce the computational cost of the classical approach of RBDO problem, the optimum safety factor (OSF) method coupled with the gPC procedure is applied to the coupled acoustic-structure systems. Numerical examples showed the effectiveness and efficiency of the OSF based on gPC for the reliability optimization of the structural-acoustic system with probabilistic random variables.

Research paper thumbnail of Experimental and numerical investigation of flexible bulging process of aluminum AA1050-H14 sheet metal with soft tools

The International Journal of Advanced Manufacturing Technology

Research paper thumbnail of Numerical modeling of uncertainty in acoustic propagation via generalized polynomial chaos

Journal of Theoretical and Applied Mechanics

This work aims at increasing the performance prediction for acoustic propagation systems that wil... more This work aims at increasing the performance prediction for acoustic propagation systems that will operate in the presence of the inevitable parameters uncertainty. In the present contribution, the finite element method is applied to solve an acoustic problem described by the Helmholz equation when the geometric and material properties present uncertainty. The influence of the uncertainty of physical parameters on the pressure field is discussed. The results using the polynomial chaos expansion method are compared with Monte Carlo simulations. It is show that uncertainty levels in the input data could result in large variability in the calculated pressure field in the domain.

Research paper thumbnail of Numerical investigation of the forming capability of bulge process by using rubber as a forming medium

The International Journal of Advanced Manufacturing Technology

A finite element simulation of flexible bulge forming of aluminum sheet metal is carried out. The... more A finite element simulation of flexible bulge forming of aluminum sheet metal is carried out. The effect of rubber pad on forming capability is studied by comparing flexible bulge to hydroforming. Based on the theory of Continuum Damage Mechanics (CDM), a local approach with fully coupling between ductile damage and an anisotropic elasto-plastic model with mixed nonlinear kinematic/isotropic hardening is introduced. The model is implemented into a user-defined material (VUMAT) subroutine for the commercial finite element code ABAQUS/Explicit. A Mooney-Rivlin theory is adopted for rubber material behavior. Comparisons between both processes in terms of thickness variation, damage occurrence, and sheet formability are conducted for different rubber shores and friction. Numerical findings are in a good correlation with experiments from literature.

Research paper thumbnail of Investigation of capillary impregnation for permeability prediction of fibrous reinforcements

Journal of Composite Materials, 2015

In thermoplastic pultrusion process, unidirectional glass fibre bundles are very often used as re... more In thermoplastic pultrusion process, unidirectional glass fibre bundles are very often used as reinforcement. This study was motivated by the industrial requirement to evolve from low viscosity thermoset resin processes to high viscosity thermoplastic polymers. The key parameters to control the impregnation process are the permeability of the fibrous reinforcement and the capillary pressure. The current study's objectives are threefold: (1) study the fibres arrangement by X-ray tomography, (2) determine the longitudinal and transversal permeabilities as well as capillary pressure to use them as input parameters of impregnation process in pultrusion and (3) carry out sensitivity analyses of the permeability measurements to the perturbation of fibre structure. To reach these purposes, two theoretical models were used to determine both axial and transversal tow permeability. The axial impregnation of aligned fibres was described by Washburn equation applied to 1D infiltration into ...

Research paper thumbnail of Thermoplastic pultrusion process: Modeling and optimal conditions for fibers impregnation

Journal of Reinforced Plastics and Composites, 2013

ABSTRACT Pultrusion is a crucial method for continuous production of fiber-reinforced composites.... more ABSTRACT Pultrusion is a crucial method for continuous production of fiber-reinforced composites. It was developed several years ago for thermosetting polymer matrices, but the challenge is now to extend it to thermoplastic matrices, with a much higher viscosity. In this paper, we propose an analysis of the parameters influencing fiber impregnation in the conditions of this process. A semi-analytical one-dimensional axisymmetric model based on Darcy’s law and Stokes equations is developed to predict the impregnation profile inside the fibrous phase in the case of a natural impregnation governed by capillary forces. Thanks to a dimensional analysis, it enables to quantify the influence of all the material and testing parameters under the assumption of a slow variation of the geometry of the impregnation die. The cases of a straight and conical dies are discussed. For the first case, an exhaustive numerical study enables to define the optimal processing conditions for a perfect impregnation. Those results are shown to be useful tools for finding an optimal pulling velocity and die length for a given fluid/fibers pair. For the second case, we show that section reductions do not improve impregnation.

Research paper thumbnail of Simple modelling of impregnation in pultrusion process of thermoplastic composites

ABSTRACT Pultrusion is a continuous process with application in the manufacture of fibre-reinforc... more ABSTRACT Pultrusion is a continuous process with application in the manufacture of fibre-reinforced composites. This work reports the impregnation process which is one of the major concerns in pultrusion. We set out to develop a model that describes the flow advancement for a thermoplastic matrix when the reinforcements pass through the die. Therefore, the influence of several processing conditions on the impregnation state has been assessed. An analytical model based upon the Darcy's law and Stokes equation was applied to describe the progression of the radial flow front through porous medium. In this investigation, a unidirectional fibrous medium is adopted and the injected fluid is considered to be Newtonian and incompressible. Results show that the geometry of the die, pulling velocity and obviously the fibres permeability are the major factors influencing the degree of wetting. This analytical methodology is a useful tool to control the matrix impregnation.

Research paper thumbnail of Finite-element analysis of errors on stress and strain measurements in dynamic tensile testing of low-ductile materials

Computers & Structures, 2010

Tensile dynamic tests are essential experiments to develop and validate constitutive equations. I... more Tensile dynamic tests are essential experiments to develop and validate constitutive equations. In this paper, we studied the errors on stress and strain measurement in dynamic tensile tests by using finite-element analysis. Two strain and one stress measures were ...

Research paper thumbnail of Etude analytique et expérimentale de l'imprégnation de composites à matrice thermoplastique dans le procédé de pultrusion

L'une des préoccupations majeures dans la production de profilés composites à matrice thermoplast... more L'une des préoccupations majeures dans la production de profilés composites à matrice thermoplastique par le procédé de pultrusion est de réussir l'imprégnation de la résine thermoplastique par le réseau de fibres de renfort, tout en réalisant une forme correcte et en conservant une excellente résistance aux chocs. En effet, l'imprégnation est un processus difficile en raison de la viscosité élevée des thermoplastiques à l'état fondu. Une étude analytique et expérimentale de l'état de l'imprégnation a été menée. Celle-ci permet de prévoir notamment la perméabilité et la pression capillaire mise en jeu lors de la progression capillaire. Les propriétés du renfort et la distribution des fibres sont mises en évidence notamment grâce à la microtomographie X.

Research paper thumbnail of Numerical study of anisotropic behavior of Aluminum alloy subjected to dynamic perforation

International Journal of Impact Engineering

Abstract A numerical investigation was carried out to analyze in details the perforation process ... more Abstract A numerical investigation was carried out to analyze in details the perforation process of target AA5754-O Aluminum plate when subjected to normal impact at low (up to 25 ms − 1 ) and moderate velocities (ranged between 25 − 50 ms − 1 ). A fully coupled elasto-visco-plastic-damage model is implemented into a user-defined material (VUMAT) subroutine for the commercial finite element code ABAQUS/Explicit. The strain rate effect is considered. Comparison between isotropic J 2 and orthotropic Hill yield criteria associated with isotropic and mixed non-linear isotropic/kinematic hardening was conducted. A parametric study of the effect of anisotropy, plate thickness and impactor nose shapes on ballistic limit and petal forming is carried out. A good agreement is found between numerical and experimental results conducted by other researchers.