Fakhreddine Dammak - Academia.edu (original) (raw)

Papers by Fakhreddine Dammak

Research paper thumbnail of Time-Dependent Deflection Responses of FG Porous Structures Subjected to Different External Pulse Loads

Journal of Vibration Engineering & Technologies

Research paper thumbnail of Buckling Response of Nanocomposite Plate Under Uniaxial In-Plane Loads

Advances in Mechanical Engineering and Mechanics II, 2021

Research paper thumbnail of A modified FSDT-based four nodes finite shell element for thermal buckling analysis of functionally graded plates and cylindrical shells

Engineering Structures, 2019

In this paper, the thermal buckling behavior of functionally graded plates and cylindrical shells... more In this paper, the thermal buckling behavior of functionally graded plates and cylindrical shells is investigated. By considering a modified First order Shear Deformation Theory, the governing equations are elaborated. The kernel idea of the proposed model consists on assuming a parabolic distribution of the transverse shear strains across the shell thickness and imposing a zero condition of the transverse shear stresses on the top and bottom surfaces of the shell structure. Four nodes shell elements are adopted to solve the thermal buckling problem. The material properties are assumed to change continuously through the thickness according to a power-law distribution. In order to highlight the potentials of the present formulation, numerical investigations are conducted and compared with results available from the literature. The computation of the critical buckling temperature of structures under non-uniform temperature rise is based on Gauss numerical integration. The effects of material compositions, power law index, thermal loading, boundary conditions and geometrical parameters of shells on the thermal buckling behavior of FGM structures are also examined.

Research paper thumbnail of Numerical and experimental study of the Erichsen test for metal stamping

Advances in Production …, 2008

In this article, we present some experimental results obtained from an ERICHSEN test. This test c... more In this article, we present some experimental results obtained from an ERICHSEN test. This test characterizes the faculty of the thin sheet stamping. In order to control the different parameters of this test, we make a confrontation between numerical results obtained with the finite elements software COSMOS/M and experimental results descended from tests realized on different material and thickness sheet metal

Research paper thumbnail of Numerical Formulation of Anisotropic Elastoplastic Behavior Coupled with Damage Model in Forming Processes

Mathematics

The present paper proposes a mathematical development of the plasticity and damage approaches to ... more The present paper proposes a mathematical development of the plasticity and damage approaches to simulate sheet metal forming processes. It focuses on the numerical prediction of the deformation of the sheet metal during the deep drawing process when a crack appears. Anisotropic plasticity constitutive equations are proposed. A fully implicit integration of the coupling constitutive equations is used and leads to two nonlinear local scalar equations that are solved by Newton’s method. The developed model allows predicting the onset of cracks in sheet metals during cold forming operations. The numerical model is implemented in ABAQUS software using user-defined subroutines, which are VUMAT and UMAT. The accuracy of the anisotropic elastoplastic model fully coupled with ductile damage is evaluated using numerical examples.

Research paper thumbnail of A Continuum Damage-Based Anisotropic Hyperelastic Fatigue Model for Short Glass Fiber Reinforced Polyamide 66

Mathematics

A phenomenological 3D anisotropic nonlinear fatigue damage model has been developed for a short g... more A phenomenological 3D anisotropic nonlinear fatigue damage model has been developed for a short glass fiber-reinforced polyamide. The model is formulated within the framework of continuum damage mechanics and is based on a proposed anisotropic hyperelastic strain energy function. The proposed model accounts for the effects of fiber content and nonlinear material behavior. The mechanical behavior of polyamide reinforced with 20% and 30% wt short glass fiber has been experimentally investigated under quasi-static and fatigue loading. Fatigue tests under bending loading are carried out on rectangular specimens cut in the parallel and perpendicular direction to the mold flow direction. The proposed fatigue damage model allows predicting the fatigue damage of composite materials reinforced with short fiberglass, considering fiber orientation and fiber content. The model is used to predict the damage evolution and the number of cycles to failure, and good agreement between predicted value...

Research paper thumbnail of Multiscale determination of the water-swelling coefficient of flax/epoxycomposites and flax yarns

HAL (Le Centre pour la Communication Scientifique Directe), Jul 1, 2019

Parmi les modifications engendrées par l'absorption d'eau dans les matériaux, l'hygro-expansion e... more Parmi les modifications engendrées par l'absorption d'eau dans les matériaux, l'hygro-expansion est un paramètre clé pour décrire les couplages hygro-mécaniques dans les composites polymères renforcés par des fibres végétales. Cependant, peu d'étude expérimentale sont proposées par la littérature. Cette étude se propose donc de déterminer, dans une approche expérimentale multi-échelle, les coefficients d'hygro-expansion des fils de lin et des composites renforcés par des fibres de lin (CRFL). Les résultats montrent un coefficient de gonflement radial des fils de lin important et nettement supérieur à celui classiquement admis dans la littérature. De même, ce papier met en évidence que les dilatations hygroscopiques des CRFL sont fortement anisotropes. L'étude montre un comportement non-linéaire des dilatations hygroscopiques des composites dans la direction des fils de chaine caractérisé par un coefficient d'hygroexpansion négatif. Les coefficients de dilatations transversaux du composite sont inférieurs à celui radial des fils de lin expliqués par l'effet bloquant de la matrice. De plus, les dilatations hygroscopiques dans la direction des fils de trame sont faibles. Ce résultat est expliqué par le coefficient d'hygro-expansion longitudinal des fils de trame négatif qui bloque les dilatations.

Research paper thumbnail of A HOSDT-Based Solid-Shell Element for Thermal Buckling Analysis of FGM Structures

Advances in Mechanical Engineering and Mechanics II, 2021

The current investigation plans to examine thermal buckling of functionally graded material (FGM)... more The current investigation plans to examine thermal buckling of functionally graded material (FGM) plates with various power index (p) and under various rise of temperature, uniform and non-uniform by utilizing a HOSDT-based solid-shell element. By applying the Higher Order Shear Deformation Theory (HOSDT) in the incompatible strain part, the shear strains guarantee a quadratic appropriation across the thickness of plate. The presented solid-shell element doesn't need a shear correction factors. Furthermore, the finite element formulation is ready to beat the locking issues due the use of the Enhanced Assumed Strain (EAS) and Assumed Natural Strain (ANS) method. The exhibition of the grew full three-dimensional component is outlined through the correlations of our outcomes with those accessible in the literature. Then, the effects of some geometric and material parameters on the critical thermal buckling temperature of shell structures are investigated.

Research paper thumbnail of Meshfree Analysis of 3-D Double Directors Shell Theory

Advances in Mechanical Engineering and Mechanics, 2019

A meshless implementation of arbitrary 3D-model based on a double directors shell element is deve... more A meshless implementation of arbitrary 3D-model based on a double directors shell element is developed in this work. The meshless technique is based on radial point interpolation method (RPIM) used for the construction of the shape functions for arbitrarily distributed nodes of the shell geometry. The high order shear deformation theory is adopted in this work in order to remove the shear correction coefficient. The convergence of the proposed model is compared to other well-known formulations found in the literature in order to outline the accuracy and performance of the present model.

Research paper thumbnail of Vibrational behavior of beams made of functionally graded materials by using a mixed formulation

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2020

This paper investigates the vibrational behavior of beams made of functionally graded materials u... more This paper investigates the vibrational behavior of beams made of functionally graded materials using a mixed formulation. Unlike the other high order shear deformation theories (HSDTs), the proposed formulation is elaborated within a double field of displacements and stresses which offers the possibility of the development of low order linear elements with enhanced accuracy. As well as, the effect of the transverse shear strains and the zero condition of the transverse shear stresses on the top and bottom surfaces are verified. The material characteristics of the beams are described via a power law distribution in order to take into account the continuous variation of the volume fraction of its constituents along the thickness direction. Numerical simulations are conducted to show the influence of power law index, slenderness ratios, and boundary conditions on natural frequencies of functionally graded beams. Results demonstrate the efficiency and the applicability of the model bas...

Research paper thumbnail of Static bending analysis of beams made of functionally graded porous materials

Mechanics Based Design of Structures and Machines, 2020

This paper constitutes a first attempt to explore the influence of porosity on bending static ana... more This paper constitutes a first attempt to explore the influence of porosity on bending static analysis of functionally graded (FG) beams using a refined mixed finite element beam model. The material properties of functionally graded porous beams are estimated using a modified power law distribution with two different types of porosity namely even and uneven distributions. The potential of the proposed model is highlighted via a comparison study. Then, a parametric study is carried out to show the effects of power law index, porosity coefficient, boundary conditions and types of porosity distributions on deflections and stresses of the studied FG beams.

Research paper thumbnail of Experimental and numerical methodology to characterize 5083-aluminium behavior considering non-associated plasticity model coupled with isotropic ductile damage

International Journal of Solids and Structures, 2021

Abstract In the present work, an elastoplastic-damage model fully coupled with the constitutive e... more Abstract In the present work, an elastoplastic-damage model fully coupled with the constitutive equations of the non-associated plasticity is developed, to enrich the existing research results on the non-associated plasticity finite element models. The yield function and the plastic potential are represented independently by two different (Hill, 1948) quadratic functions to describe the anisotropic behavior of 5083-aluminium alloy. The current model develops a first attempt to establish a general formulation with two ductile degradation functions, one for elasticity and the other for plasticity, with variable degradation coefficients. Further, the elastoplastic behavior of 5083-aluminium alloy is determined through uniaxial tensile tests, so that the anisotropic, the isotropic hardening and the damage parameters are acquired. Experimental-numerical confrontation proves the reliability of the current formulation to describe the behavior of 5083-aluminium alloy with good accuracy. Furthermore, a novel numerical optimization procedure is firstly used to analytically identify Lemaitre damage parameters in order to limit the non-unicity of these parameters. The adopted optimization procedure offers a compromise between good accuracy and low computational time to determine the damage parameters.

Research paper thumbnail of SPIF process of axisymmetric parts made of AA1060-H14 aluminum alloy tested on  2 axis-NC lathe machine

This paper deals with an experimental and numerical study focused on the SPIF process of a dome p... more This paper deals with an experimental and numerical study focused on the SPIF process of a dome part manufactured by means of a 2-axis NC lathe machine. The main objective is to enhance the understanding of a set of parameters in connection with ISF operations applied to this type of machine unusually used in incremental forming processes, despite the high degree of development of NC lathe machines. Nowadays 4 and 5 axis lathe centers are widely used in industrial applications. This makes NC lathe machines useful in SPIF process especially in the case of axisymmetric parts. The present results, covering thinning, appearance of cracks, surface quality and FLD diagram; prove the efficiency of NC turning machines to perform SPIF application of parts commonly manufactured by a 3-axis NC milling machine.

Research paper thumbnail of A Characterization of the Damage Process under Buckling Load in Composite Reinforced by Flax Fibres

Journal of Composites Science, 2020

The purpose of this work is to analyze the damage process resulting from buckling load applied on... more The purpose of this work is to analyze the damage process resulting from buckling load applied on composites reinforced by flax fibre. Continous buckling test was performed on specimens until cracks appeared on their outer face. This test was monitored with an acoustic emission system. The high sensitivity of this method allows the detection of any process or mechanism generating sound waves. Moreover, this technic has the advantage of not causing contact in the deformed zone and thus to overcome the parasitic damage that may result from the stress concentrations in these areas. A multiparametric analysis is used to identify the acoustic signatures corresponding to each damage mechanism involved in the materials, and then follow their evolution in order to identify the most critical mechanisms leading to the final breakage of the material. The presence of these damage mechanisms was confirmed post-test by microscopic observations. Three orientations of laminate specimens (0°, 90° an...

Research paper thumbnail of An efficient ABAQUS solid shell element implementation for low velocity impact analysis of FGM plates

Engineering with Computers, 2020

The main objective of this paper is to develop a numerical model susceptible to solve the numeric... more The main objective of this paper is to develop a numerical model susceptible to solve the numerical locking problems that may appear when applying the conventional solid and shell finite elements of ABAQUS. This model is based on an hexahedral solid shell element. The formulation of this element relay on the combination of the Enhanced Assumed Strain (EAS) and Assumed Natural Strain (ANS) methods with modified FSDT. The developed element is implemented into the ABAQUS user element (UEL) interface. The performance of this element is demonstrated by different benchmark tests from literature. Our contribution consists on applying a single solid shell element through the thickness direction to predict the low velocity impact behavior on FGM circular plates.

Research paper thumbnail of Buckling analysis of carbon nanotube reinforced FG shells using an efficient solid-shell element based on a modified FSDT

Thin-Walled Structures, 2019

This study investigates buckling behaviors of functionally graded carbon nanotube-reinforced comp... more This study investigates buckling behaviors of functionally graded carbon nanotube-reinforced composites (FG-CNTRC) shells using a modified first-order enhanced solid-shell element formulation. On that account, a parabolic shear strain distribution through the shell thickness in the compatible strain part is proposed. In fact, the shear correction factors are no longer needed. Five kinds of single-walled carbon nanotubes (SWCNTs) distribution through the thickness of layers are considered, namely, uniform (UD) and functionally graded (FG) symmetric and asymmetric. The buckling behavior of FG-CNTRC plate under uniaxial compressive pressure and FG-CNTRC cylindrical shell under external pressure and axial compression are considered. Comparisons of our numerical results with those reported by other investigators are presented in order to compare different formulations and to illustrate the performance of the developed solid-shell element. The result of the buckling behavior of CNTRC structure makes the present formulation appropriate for a wide range of structure plates and shells. Then, the effects of some geometrical and material parameters on the critical buckling load of shell structures are investigated. Recent years have been marked by keen interest in the buckling and

Research paper thumbnail of Numerical Analysis of Geometrically Non-Linear Behavior of Functionally Graded Shells

Latin American Journal of Solids and Structures, 2017

In this paper, a geometrically nonlinear analysis of functionally graded material (FGM) shells is... more In this paper, a geometrically nonlinear analysis of functionally graded material (FGM) shells is investigated using Abaqus software. A user defined subroutine (UMAT) is developed and implemented in Abaqus/Standard to study the FG shells in large displacements and rotations. The material properties are introduced according to the integration points in Abaqus via the UMAT subroutine. The predictions of static response of several non-trivial structure problems are compared to some reference solutions in order to verify the accuracy and the effectiveness of the new developed nonlinear solution procedures. All the results indicate very good performance in comparison with references.

Research paper thumbnail of Anisotropic Visco-Elastoplastic Modeling of Quasi-Unidirectional Flax Fiber Reinforced Epoxy Behavior: An Investigation on Low-Velocity Impact Response

Journal of Renewable Materials, 2018

Based on experimental test results, flax fiber reinforced polymer composites are characterized by... more Based on experimental test results, flax fiber reinforced polymer composites are characterized by nonlinear visco-elastoplastic behavior. The aim of this work is to model the quasi-unidirectional flax fiber reinforced composite behavior through a three dimensional formulation with orthotropic elasticity and orthotropic plasticity using Hill criterion. The isotropic hardening and Johnson Cook parameters are identified from unidirectional tensile tests at different strain rates. The adjustment of Hill's yield criterion is developed based on yield stresses obtained in tensile tests at different directions. The numerical integration of the constitutive equations is implemented in a user-defined material, UMAT subroutines for the commercial finite element code ABAQUS. Once model parameters are identified using tensile tests, the model needs to be validated by confronting it with other experimental results. That is why experimental and numerical three-point bending tests are carried out in order to validate the proposed model with tests that have not served for the identification. Finally, a numerical parametric study on low velocity impact of a flax/epoxy composite circular plate is investigated.

Research paper thumbnail of Dynamic analysis of functionally graded carbon nanotubes-reinforced plate and shell structures using a double directors finite shell element

Aerospace Science and Technology, 2018

Please cite this article in press as: A. Frikha et al., Dynamic analysis of functionally graded c... more Please cite this article in press as: A. Frikha et al., Dynamic analysis of functionally graded carbon nanotubes-reinforced plate and shell structures using a double directors finite shell element,

Research paper thumbnail of An improved enhanced solid shell element for static and buckling analysis of shell structures

Mechanics & Industry, 2016

This paper presents an improved higher order solid shell element for static and buckling analysis... more This paper presents an improved higher order solid shell element for static and buckling analysis of laminated composite structures based on the enhanced assumed strain (EAS). The transverse shear strain is divided into two parts: the first one is independent of the thickness coordinate and formulated by the assumed natural strain (ANS) method; the second part is an enhancing part, which ensures a quadratic distribution through the thickness. This allows removing the shear correction factors and improves the accuracy of transverse shear stresses. In addition, volumetric locking is completely avoided by using the optimal parameters in the EAS method. The formulated finite element is implemented to study the static and buckling behavior of shell structures and to investigate the influence of some parameters on the buckling load. Comparisons of numerical results with those extracted from literature show the acceptable performance of the developed element.

Research paper thumbnail of Time-Dependent Deflection Responses of FG Porous Structures Subjected to Different External Pulse Loads

Journal of Vibration Engineering & Technologies

Research paper thumbnail of Buckling Response of Nanocomposite Plate Under Uniaxial In-Plane Loads

Advances in Mechanical Engineering and Mechanics II, 2021

Research paper thumbnail of A modified FSDT-based four nodes finite shell element for thermal buckling analysis of functionally graded plates and cylindrical shells

Engineering Structures, 2019

In this paper, the thermal buckling behavior of functionally graded plates and cylindrical shells... more In this paper, the thermal buckling behavior of functionally graded plates and cylindrical shells is investigated. By considering a modified First order Shear Deformation Theory, the governing equations are elaborated. The kernel idea of the proposed model consists on assuming a parabolic distribution of the transverse shear strains across the shell thickness and imposing a zero condition of the transverse shear stresses on the top and bottom surfaces of the shell structure. Four nodes shell elements are adopted to solve the thermal buckling problem. The material properties are assumed to change continuously through the thickness according to a power-law distribution. In order to highlight the potentials of the present formulation, numerical investigations are conducted and compared with results available from the literature. The computation of the critical buckling temperature of structures under non-uniform temperature rise is based on Gauss numerical integration. The effects of material compositions, power law index, thermal loading, boundary conditions and geometrical parameters of shells on the thermal buckling behavior of FGM structures are also examined.

Research paper thumbnail of Numerical and experimental study of the Erichsen test for metal stamping

Advances in Production …, 2008

In this article, we present some experimental results obtained from an ERICHSEN test. This test c... more In this article, we present some experimental results obtained from an ERICHSEN test. This test characterizes the faculty of the thin sheet stamping. In order to control the different parameters of this test, we make a confrontation between numerical results obtained with the finite elements software COSMOS/M and experimental results descended from tests realized on different material and thickness sheet metal

Research paper thumbnail of Numerical Formulation of Anisotropic Elastoplastic Behavior Coupled with Damage Model in Forming Processes

Mathematics

The present paper proposes a mathematical development of the plasticity and damage approaches to ... more The present paper proposes a mathematical development of the plasticity and damage approaches to simulate sheet metal forming processes. It focuses on the numerical prediction of the deformation of the sheet metal during the deep drawing process when a crack appears. Anisotropic plasticity constitutive equations are proposed. A fully implicit integration of the coupling constitutive equations is used and leads to two nonlinear local scalar equations that are solved by Newton’s method. The developed model allows predicting the onset of cracks in sheet metals during cold forming operations. The numerical model is implemented in ABAQUS software using user-defined subroutines, which are VUMAT and UMAT. The accuracy of the anisotropic elastoplastic model fully coupled with ductile damage is evaluated using numerical examples.

Research paper thumbnail of A Continuum Damage-Based Anisotropic Hyperelastic Fatigue Model for Short Glass Fiber Reinforced Polyamide 66

Mathematics

A phenomenological 3D anisotropic nonlinear fatigue damage model has been developed for a short g... more A phenomenological 3D anisotropic nonlinear fatigue damage model has been developed for a short glass fiber-reinforced polyamide. The model is formulated within the framework of continuum damage mechanics and is based on a proposed anisotropic hyperelastic strain energy function. The proposed model accounts for the effects of fiber content and nonlinear material behavior. The mechanical behavior of polyamide reinforced with 20% and 30% wt short glass fiber has been experimentally investigated under quasi-static and fatigue loading. Fatigue tests under bending loading are carried out on rectangular specimens cut in the parallel and perpendicular direction to the mold flow direction. The proposed fatigue damage model allows predicting the fatigue damage of composite materials reinforced with short fiberglass, considering fiber orientation and fiber content. The model is used to predict the damage evolution and the number of cycles to failure, and good agreement between predicted value...

Research paper thumbnail of Multiscale determination of the water-swelling coefficient of flax/epoxycomposites and flax yarns

HAL (Le Centre pour la Communication Scientifique Directe), Jul 1, 2019

Parmi les modifications engendrées par l'absorption d'eau dans les matériaux, l'hygro-expansion e... more Parmi les modifications engendrées par l'absorption d'eau dans les matériaux, l'hygro-expansion est un paramètre clé pour décrire les couplages hygro-mécaniques dans les composites polymères renforcés par des fibres végétales. Cependant, peu d'étude expérimentale sont proposées par la littérature. Cette étude se propose donc de déterminer, dans une approche expérimentale multi-échelle, les coefficients d'hygro-expansion des fils de lin et des composites renforcés par des fibres de lin (CRFL). Les résultats montrent un coefficient de gonflement radial des fils de lin important et nettement supérieur à celui classiquement admis dans la littérature. De même, ce papier met en évidence que les dilatations hygroscopiques des CRFL sont fortement anisotropes. L'étude montre un comportement non-linéaire des dilatations hygroscopiques des composites dans la direction des fils de chaine caractérisé par un coefficient d'hygroexpansion négatif. Les coefficients de dilatations transversaux du composite sont inférieurs à celui radial des fils de lin expliqués par l'effet bloquant de la matrice. De plus, les dilatations hygroscopiques dans la direction des fils de trame sont faibles. Ce résultat est expliqué par le coefficient d'hygro-expansion longitudinal des fils de trame négatif qui bloque les dilatations.

Research paper thumbnail of A HOSDT-Based Solid-Shell Element for Thermal Buckling Analysis of FGM Structures

Advances in Mechanical Engineering and Mechanics II, 2021

The current investigation plans to examine thermal buckling of functionally graded material (FGM)... more The current investigation plans to examine thermal buckling of functionally graded material (FGM) plates with various power index (p) and under various rise of temperature, uniform and non-uniform by utilizing a HOSDT-based solid-shell element. By applying the Higher Order Shear Deformation Theory (HOSDT) in the incompatible strain part, the shear strains guarantee a quadratic appropriation across the thickness of plate. The presented solid-shell element doesn't need a shear correction factors. Furthermore, the finite element formulation is ready to beat the locking issues due the use of the Enhanced Assumed Strain (EAS) and Assumed Natural Strain (ANS) method. The exhibition of the grew full three-dimensional component is outlined through the correlations of our outcomes with those accessible in the literature. Then, the effects of some geometric and material parameters on the critical thermal buckling temperature of shell structures are investigated.

Research paper thumbnail of Meshfree Analysis of 3-D Double Directors Shell Theory

Advances in Mechanical Engineering and Mechanics, 2019

A meshless implementation of arbitrary 3D-model based on a double directors shell element is deve... more A meshless implementation of arbitrary 3D-model based on a double directors shell element is developed in this work. The meshless technique is based on radial point interpolation method (RPIM) used for the construction of the shape functions for arbitrarily distributed nodes of the shell geometry. The high order shear deformation theory is adopted in this work in order to remove the shear correction coefficient. The convergence of the proposed model is compared to other well-known formulations found in the literature in order to outline the accuracy and performance of the present model.

Research paper thumbnail of Vibrational behavior of beams made of functionally graded materials by using a mixed formulation

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2020

This paper investigates the vibrational behavior of beams made of functionally graded materials u... more This paper investigates the vibrational behavior of beams made of functionally graded materials using a mixed formulation. Unlike the other high order shear deformation theories (HSDTs), the proposed formulation is elaborated within a double field of displacements and stresses which offers the possibility of the development of low order linear elements with enhanced accuracy. As well as, the effect of the transverse shear strains and the zero condition of the transverse shear stresses on the top and bottom surfaces are verified. The material characteristics of the beams are described via a power law distribution in order to take into account the continuous variation of the volume fraction of its constituents along the thickness direction. Numerical simulations are conducted to show the influence of power law index, slenderness ratios, and boundary conditions on natural frequencies of functionally graded beams. Results demonstrate the efficiency and the applicability of the model bas...

Research paper thumbnail of Static bending analysis of beams made of functionally graded porous materials

Mechanics Based Design of Structures and Machines, 2020

This paper constitutes a first attempt to explore the influence of porosity on bending static ana... more This paper constitutes a first attempt to explore the influence of porosity on bending static analysis of functionally graded (FG) beams using a refined mixed finite element beam model. The material properties of functionally graded porous beams are estimated using a modified power law distribution with two different types of porosity namely even and uneven distributions. The potential of the proposed model is highlighted via a comparison study. Then, a parametric study is carried out to show the effects of power law index, porosity coefficient, boundary conditions and types of porosity distributions on deflections and stresses of the studied FG beams.

Research paper thumbnail of Experimental and numerical methodology to characterize 5083-aluminium behavior considering non-associated plasticity model coupled with isotropic ductile damage

International Journal of Solids and Structures, 2021

Abstract In the present work, an elastoplastic-damage model fully coupled with the constitutive e... more Abstract In the present work, an elastoplastic-damage model fully coupled with the constitutive equations of the non-associated plasticity is developed, to enrich the existing research results on the non-associated plasticity finite element models. The yield function and the plastic potential are represented independently by two different (Hill, 1948) quadratic functions to describe the anisotropic behavior of 5083-aluminium alloy. The current model develops a first attempt to establish a general formulation with two ductile degradation functions, one for elasticity and the other for plasticity, with variable degradation coefficients. Further, the elastoplastic behavior of 5083-aluminium alloy is determined through uniaxial tensile tests, so that the anisotropic, the isotropic hardening and the damage parameters are acquired. Experimental-numerical confrontation proves the reliability of the current formulation to describe the behavior of 5083-aluminium alloy with good accuracy. Furthermore, a novel numerical optimization procedure is firstly used to analytically identify Lemaitre damage parameters in order to limit the non-unicity of these parameters. The adopted optimization procedure offers a compromise between good accuracy and low computational time to determine the damage parameters.

Research paper thumbnail of SPIF process of axisymmetric parts made of AA1060-H14 aluminum alloy tested on  2 axis-NC lathe machine

This paper deals with an experimental and numerical study focused on the SPIF process of a dome p... more This paper deals with an experimental and numerical study focused on the SPIF process of a dome part manufactured by means of a 2-axis NC lathe machine. The main objective is to enhance the understanding of a set of parameters in connection with ISF operations applied to this type of machine unusually used in incremental forming processes, despite the high degree of development of NC lathe machines. Nowadays 4 and 5 axis lathe centers are widely used in industrial applications. This makes NC lathe machines useful in SPIF process especially in the case of axisymmetric parts. The present results, covering thinning, appearance of cracks, surface quality and FLD diagram; prove the efficiency of NC turning machines to perform SPIF application of parts commonly manufactured by a 3-axis NC milling machine.

Research paper thumbnail of A Characterization of the Damage Process under Buckling Load in Composite Reinforced by Flax Fibres

Journal of Composites Science, 2020

The purpose of this work is to analyze the damage process resulting from buckling load applied on... more The purpose of this work is to analyze the damage process resulting from buckling load applied on composites reinforced by flax fibre. Continous buckling test was performed on specimens until cracks appeared on their outer face. This test was monitored with an acoustic emission system. The high sensitivity of this method allows the detection of any process or mechanism generating sound waves. Moreover, this technic has the advantage of not causing contact in the deformed zone and thus to overcome the parasitic damage that may result from the stress concentrations in these areas. A multiparametric analysis is used to identify the acoustic signatures corresponding to each damage mechanism involved in the materials, and then follow their evolution in order to identify the most critical mechanisms leading to the final breakage of the material. The presence of these damage mechanisms was confirmed post-test by microscopic observations. Three orientations of laminate specimens (0°, 90° an...

Research paper thumbnail of An efficient ABAQUS solid shell element implementation for low velocity impact analysis of FGM plates

Engineering with Computers, 2020

The main objective of this paper is to develop a numerical model susceptible to solve the numeric... more The main objective of this paper is to develop a numerical model susceptible to solve the numerical locking problems that may appear when applying the conventional solid and shell finite elements of ABAQUS. This model is based on an hexahedral solid shell element. The formulation of this element relay on the combination of the Enhanced Assumed Strain (EAS) and Assumed Natural Strain (ANS) methods with modified FSDT. The developed element is implemented into the ABAQUS user element (UEL) interface. The performance of this element is demonstrated by different benchmark tests from literature. Our contribution consists on applying a single solid shell element through the thickness direction to predict the low velocity impact behavior on FGM circular plates.

Research paper thumbnail of Buckling analysis of carbon nanotube reinforced FG shells using an efficient solid-shell element based on a modified FSDT

Thin-Walled Structures, 2019

This study investigates buckling behaviors of functionally graded carbon nanotube-reinforced comp... more This study investigates buckling behaviors of functionally graded carbon nanotube-reinforced composites (FG-CNTRC) shells using a modified first-order enhanced solid-shell element formulation. On that account, a parabolic shear strain distribution through the shell thickness in the compatible strain part is proposed. In fact, the shear correction factors are no longer needed. Five kinds of single-walled carbon nanotubes (SWCNTs) distribution through the thickness of layers are considered, namely, uniform (UD) and functionally graded (FG) symmetric and asymmetric. The buckling behavior of FG-CNTRC plate under uniaxial compressive pressure and FG-CNTRC cylindrical shell under external pressure and axial compression are considered. Comparisons of our numerical results with those reported by other investigators are presented in order to compare different formulations and to illustrate the performance of the developed solid-shell element. The result of the buckling behavior of CNTRC structure makes the present formulation appropriate for a wide range of structure plates and shells. Then, the effects of some geometrical and material parameters on the critical buckling load of shell structures are investigated. Recent years have been marked by keen interest in the buckling and

Research paper thumbnail of Numerical Analysis of Geometrically Non-Linear Behavior of Functionally Graded Shells

Latin American Journal of Solids and Structures, 2017

In this paper, a geometrically nonlinear analysis of functionally graded material (FGM) shells is... more In this paper, a geometrically nonlinear analysis of functionally graded material (FGM) shells is investigated using Abaqus software. A user defined subroutine (UMAT) is developed and implemented in Abaqus/Standard to study the FG shells in large displacements and rotations. The material properties are introduced according to the integration points in Abaqus via the UMAT subroutine. The predictions of static response of several non-trivial structure problems are compared to some reference solutions in order to verify the accuracy and the effectiveness of the new developed nonlinear solution procedures. All the results indicate very good performance in comparison with references.

Research paper thumbnail of Anisotropic Visco-Elastoplastic Modeling of Quasi-Unidirectional Flax Fiber Reinforced Epoxy Behavior: An Investigation on Low-Velocity Impact Response

Journal of Renewable Materials, 2018

Based on experimental test results, flax fiber reinforced polymer composites are characterized by... more Based on experimental test results, flax fiber reinforced polymer composites are characterized by nonlinear visco-elastoplastic behavior. The aim of this work is to model the quasi-unidirectional flax fiber reinforced composite behavior through a three dimensional formulation with orthotropic elasticity and orthotropic plasticity using Hill criterion. The isotropic hardening and Johnson Cook parameters are identified from unidirectional tensile tests at different strain rates. The adjustment of Hill's yield criterion is developed based on yield stresses obtained in tensile tests at different directions. The numerical integration of the constitutive equations is implemented in a user-defined material, UMAT subroutines for the commercial finite element code ABAQUS. Once model parameters are identified using tensile tests, the model needs to be validated by confronting it with other experimental results. That is why experimental and numerical three-point bending tests are carried out in order to validate the proposed model with tests that have not served for the identification. Finally, a numerical parametric study on low velocity impact of a flax/epoxy composite circular plate is investigated.

Research paper thumbnail of Dynamic analysis of functionally graded carbon nanotubes-reinforced plate and shell structures using a double directors finite shell element

Aerospace Science and Technology, 2018

Please cite this article in press as: A. Frikha et al., Dynamic analysis of functionally graded c... more Please cite this article in press as: A. Frikha et al., Dynamic analysis of functionally graded carbon nanotubes-reinforced plate and shell structures using a double directors finite shell element,

Research paper thumbnail of An improved enhanced solid shell element for static and buckling analysis of shell structures

Mechanics & Industry, 2016

This paper presents an improved higher order solid shell element for static and buckling analysis... more This paper presents an improved higher order solid shell element for static and buckling analysis of laminated composite structures based on the enhanced assumed strain (EAS). The transverse shear strain is divided into two parts: the first one is independent of the thickness coordinate and formulated by the assumed natural strain (ANS) method; the second part is an enhancing part, which ensures a quadratic distribution through the thickness. This allows removing the shear correction factors and improves the accuracy of transverse shear stresses. In addition, volumetric locking is completely avoided by using the optimal parameters in the EAS method. The formulated finite element is implemented to study the static and buckling behavior of shell structures and to investigate the influence of some parameters on the buckling load. Comparisons of numerical results with those extracted from literature show the acceptable performance of the developed element.