https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Sun, 12 Jul 2026 12:20:51 GMT 2026-07-12T12:20:51Z http://hdl.handle.net/10985/10496 Endommagement en fatigue du PA66 renforcé par des fibres de verre courtes : modélisation micromécanique et stratégie d'identification multi - échelles DESPRINGRE, Nicolas; CHEMISKY, Yves; FITOUSSI, Joseph; MERAGHNI, Fodil Cet article présente un modèle micromécanique visco-endommageable pour les composites à matrice thermoplastique renforcée par des fibres de verre courtes et soumis à un chargement en fatigue. L'approche multi-échelles développée est fondée sur la méthode de Mori-Tanaka, modifiée afin d'inclure des inclusions enrobées et l'évolution des mécanismes d'endommagement à l'échelle microscopique. Le modèle développé intègre les cinétiques d'endommagement tout en tenant compte de la viscoélasticité matricielle et de la microstucture. La prise en compte de ces derniers se base sur des travaux précédemment menés par les auteurs sur le PA66/GF30 moulé par injection [3-5]. Des scénarios d'endommagement ont été proposés et regroupent trois mécanismes : la décohésion interfaciale fibre­ matrice, la fissuration matricielle et les ruptures de fibres. Chaque mécanisme d'endommagement est associé à une loi d'évolution dépendant des champs de contraintes à l'échelle microscopique. La loi constitutive du volume élémentaire représentatif est implémentée dans Abaqus en tant qu'User MATerial subroutine. L'identification du modèle se fait par méthodes inverses, bénéficiant ainsi des résultats multi-échelles précédemment obtenus à l'aide de tests in-situ au MEB ou à partir de l'analyse quantitative et qualitative de données issus de la microtomographie. La validation expérimentale est réalisée par des tests en fatigue contrôlés en déformation. Thu, 01 Jan 2015 00:00:00 GMT http://hdl.handle.net/10985/10496 2015-01-01T00:00:00Z DESPRINGRE, Nicolas CHEMISKY, Yves FITOUSSI, Joseph MERAGHNI, Fodil Cet article présente un modèle micromécanique visco-endommageable pour les composites à matrice thermoplastique renforcée par des fibres de verre courtes et soumis à un chargement en fatigue. L'approche multi-échelles développée est fondée sur la méthode de Mori-Tanaka, modifiée afin d'inclure des inclusions enrobées et l'évolution des mécanismes d'endommagement à l'échelle microscopique. Le modèle développé intègre les cinétiques d'endommagement tout en tenant compte de la viscoélasticité matricielle et de la microstucture. La prise en compte de ces derniers se base sur des travaux précédemment menés par les auteurs sur le PA66/GF30 moulé par injection [3-5]. Des scénarios d'endommagement ont été proposés et regroupent trois mécanismes : la décohésion interfaciale fibre­ matrice, la fissuration matricielle et les ruptures de fibres. Chaque mécanisme d'endommagement est associé à une loi d'évolution dépendant des champs de contraintes à l'échelle microscopique. La loi constitutive du volume élémentaire représentatif est implémentée dans Abaqus en tant qu'User MATerial subroutine. L'identification du modèle se fait par méthodes inverses, bénéficiant ainsi des résultats multi-échelles précédemment obtenus à l'aide de tests in-situ au MEB ou à partir de l'analyse quantitative et qualitative de données issus de la microtomographie. La validation expérimentale est réalisée par des tests en fatigue contrôlés en déformation. http://hdl.handle.net/10985/10354 Fatigue damage in short glass fiber reinforced PA66: Micromechanical modeling and multiscale identification approach DESPRINGRE, Nicolas; CHEMISKY, Yves; MERAGHNI, Fodil; FITOUSSI, Joseph; ROBERT, Gilles The paper presents a new micromechanical high cycle fatigue visco-damage model for short glass fiber reinforced thermoplastic composites, namely: PA66/GF30. This material, extensively used for automotive applications, has a specific microstructure which is induced by the injection process. The multi-scale developed approach is a modified Mori-Tanaka method that includes coated reinforcements and the evolution of micro-scale damage processes. The description of the damage processes is based on the experimental investigations of damage mechanisms previously performed by the authors and presented elsewhere [M.F. Arif et al. "In situ damage mechanisms investigation of PA66/GF30 composite: Effect of relative humidity." Composites Part B: Engineering, Volume 61: 55-65, 2014]. Damage chronologies have been proposed involving three different local degradation processes: fiber-matrix interface debonding/coating degradation, matrix microcracking and fiber breakage. Their occurrence strongly depends on the microstructure and the moisture content. The developed model integrates these damage kinetics and accounts for the complex matrix viscoelasticity and the reinforcement orientation distributions induced by the process. Each damage mechanism is introduced through an evolution law involving local stress fields computed at the microscale. The developed constitutive law at the representative volume element scale is implemented into the finite element code Abaqus using a User MATerial subroutine. The model identification is performed via reverse engineering, taking advantage of the multiscale experimental results: in-situ SEM tests as well as quantitative and qualitative μCT investigations. Experimental validation is achieved using high cycle strain controlled fatigue tests. Thu, 01 Jan 2015 00:00:00 GMT http://hdl.handle.net/10985/10354 2015-01-01T00:00:00Z DESPRINGRE, Nicolas CHEMISKY, Yves MERAGHNI, Fodil FITOUSSI, Joseph ROBERT, Gilles The paper presents a new micromechanical high cycle fatigue visco-damage model for short glass fiber reinforced thermoplastic composites, namely: PA66/GF30. This material, extensively used for automotive applications, has a specific microstructure which is induced by the injection process. The multi-scale developed approach is a modified Mori-Tanaka method that includes coated reinforcements and the evolution of micro-scale damage processes. The description of the damage processes is based on the experimental investigations of damage mechanisms previously performed by the authors and presented elsewhere [M.F. Arif et al. "In situ damage mechanisms investigation of PA66/GF30 composite: Effect of relative humidity." Composites Part B: Engineering, Volume 61: 55-65, 2014]. Damage chronologies have been proposed involving three different local degradation processes: fiber-matrix interface debonding/coating degradation, matrix microcracking and fiber breakage. Their occurrence strongly depends on the microstructure and the moisture content. The developed model integrates these damage kinetics and accounts for the complex matrix viscoelasticity and the reinforcement orientation distributions induced by the process. Each damage mechanism is introduced through an evolution law involving local stress fields computed at the microscale. The developed constitutive law at the representative volume element scale is implemented into the finite element code Abaqus using a User MATerial subroutine. The model identification is performed via reverse engineering, taking advantage of the multiscale experimental results: in-situ SEM tests as well as quantitative and qualitative μCT investigations. Experimental validation is achieved using high cycle strain controlled fatigue tests. http://hdl.handle.net/10985/11144 Micromechanical modeling of damage and load transfer in particulate composites with partially debonded interface DESPRINGRE, Nicolas; CHEMISKY, Yves; BONNAY, Kevin; MERAGHNI, Fodil A new micromechanical damage model accounting for progressive interface debonding is developed for composite materials. It consists of an original evolution law of the damage at the interface and an appropriate load transfer law at the matrix-fiber interface integrated into a generalized incremental Mori–Tanaka homogenization scheme. The interface damage evolution is driven by the interfacial stress state while the load transfer is obtained from a new model inspired by the shear lag model. Specifically, such damage evolution is supported by experimental microscopic observations for short glass fiber reinforced polyamide-66. The proposed model is validated based on numerical reference solutions provided from finite element analyses of a representative unit cell of a composite, where imperfect interfaces are represented using cohesive elements. A further comparison with experimental data proves that the proposed model is an alternative to micromechanical models involving weak interfaces in the case of spherical reinforcements. It is shown that the proposed model is able to accurately reproduce the non-linear effective response of composite materials for a broad range of reinforcement shapes, including spherical particles and matrix mechanical properties. Fri, 01 Jan 2016 00:00:00 GMT http://hdl.handle.net/10985/11144 2016-01-01T00:00:00Z DESPRINGRE, Nicolas CHEMISKY, Yves BONNAY, Kevin MERAGHNI, Fodil A new micromechanical damage model accounting for progressive interface debonding is developed for composite materials. It consists of an original evolution law of the damage at the interface and an appropriate load transfer law at the matrix-fiber interface integrated into a generalized incremental Mori–Tanaka homogenization scheme. The interface damage evolution is driven by the interfacial stress state while the load transfer is obtained from a new model inspired by the shear lag model. Specifically, such damage evolution is supported by experimental microscopic observations for short glass fiber reinforced polyamide-66. The proposed model is validated based on numerical reference solutions provided from finite element analyses of a representative unit cell of a composite, where imperfect interfaces are represented using cohesive elements. A further comparison with experimental data proves that the proposed model is an alternative to micromechanical models involving weak interfaces in the case of spherical reinforcements. It is shown that the proposed model is able to accurately reproduce the non-linear effective response of composite materials for a broad range of reinforcement shapes, including spherical particles and matrix mechanical properties. http://hdl.handle.net/10985/11174 Interfacial damage and load transfermodeling in short fiber reinforced composites BONNAY, Kevin; DESPRINGRE, Nicolas; CHEMISKY, Yves; MERAGHNI, Fodil Due to the compromise between their thermomechanical properties and low density, Short Fiber Reinforced Polyamides (SFRP) present a good alternative to metals for automotive structural components. The microstructure of such materials, combined with the matrix sensitivity to environmental conditions, has a strong impact on their overall behavior and the related damage. A new multi-scale modelling strategy is proposed, based on the experimental observations of interfacial damage evolution for PA66-GF30 composites. Three main key-points have been integrated to this approach: an original damage evolution law at the interface, an appropriate load transfer law at the matrix-fiber interface, and a homogenization strategy founded on the generalized Mori-Tanaka scheme. The damage evolution law is driven by a local probabilistic criterion based on the interfacial stress field estimation. This type of evolution depends on the maximal local damage rate at the fiber/matrix interface, determined from a numerical evaluation at several points of the interface surrounding the inclusion. It is then coupled with a load transfer law formulated according to a modified shear lag model (SLM). The developed model is assessed with a finite element (FE) computation integrating cohesive elements at the matrix-fiber interface. The FE unit cell consists in a periodic media (hexagonal array) with periodic boundary conditions. The fiber-matrix interface integrates cohesive elements, with a cohesive law driven by a Paulino-Park-Roesler (PPR) potential-based formulation. The latter has been proven to be suitable for the 3D modeling of interface in reinforced composites. The proposed approach is able to accurately capture the non-linear behavior of short fiber reinforced polyamide composites accounting for interfacial damage. Fri, 01 Jan 2016 00:00:00 GMT http://hdl.handle.net/10985/11174 2016-01-01T00:00:00Z BONNAY, Kevin DESPRINGRE, Nicolas CHEMISKY, Yves MERAGHNI, Fodil Due to the compromise between their thermomechanical properties and low density, Short Fiber Reinforced Polyamides (SFRP) present a good alternative to metals for automotive structural components. The microstructure of such materials, combined with the matrix sensitivity to environmental conditions, has a strong impact on their overall behavior and the related damage. A new multi-scale modelling strategy is proposed, based on the experimental observations of interfacial damage evolution for PA66-GF30 composites. Three main key-points have been integrated to this approach: an original damage evolution law at the interface, an appropriate load transfer law at the matrix-fiber interface, and a homogenization strategy founded on the generalized Mori-Tanaka scheme. The damage evolution law is driven by a local probabilistic criterion based on the interfacial stress field estimation. This type of evolution depends on the maximal local damage rate at the fiber/matrix interface, determined from a numerical evaluation at several points of the interface surrounding the inclusion. It is then coupled with a load transfer law formulated according to a modified shear lag model (SLM). The developed model is assessed with a finite element (FE) computation integrating cohesive elements at the matrix-fiber interface. The FE unit cell consists in a periodic media (hexagonal array) with periodic boundary conditions. The fiber-matrix interface integrates cohesive elements, with a cohesive law driven by a Paulino-Park-Roesler (PPR) potential-based formulation. The latter has been proven to be suitable for the 3D modeling of interface in reinforced composites. The proposed approach is able to accurately capture the non-linear behavior of short fiber reinforced polyamide composites accounting for interfacial damage. http://hdl.handle.net/10985/10258 Multi-scale viscoelastic damage model of short glass fiber reinforced thermoplastics under fatigue loading DESPRINGRE, Nicolas; CHEMISKY, Yves; ARIF, Muhamad Fatikul; ROBERT, Gilles; MERAGHNI, Fodil This work presents a new micromechanical fatigue damage model for reinforced thermoplastic composites. The study aims at modeling high cycle fatigue damage of a short glass fiber reinforced polyamide-66. The developed approach is a modified Mori-Tanaka method that includes coated reinforcements and microscale damage processes. The model takes into account the nonlinear matrix viscoelasticity and the damage mechanisms evolution. The latter is based on the experimental damage investigation previously performed by the authors and presented elsewhere. Damage chronologies have been proposed involving three different local processes: fiber-matrix interface debonding/coating degradation, matrix microcracking and fiber breakage. Each damage mechanism is introduced through an evolution law coupled to local stress fields computed at the microscale. The first numerical results show capability of the developed model to predict the fatigue damage accumulation of the macroscopic homogenized composite material. Wed, 01 Jan 2014 00:00:00 GMT http://hdl.handle.net/10985/10258 2014-01-01T00:00:00Z DESPRINGRE, Nicolas CHEMISKY, Yves ARIF, Muhamad Fatikul ROBERT, Gilles MERAGHNI, Fodil This work presents a new micromechanical fatigue damage model for reinforced thermoplastic composites. The study aims at modeling high cycle fatigue damage of a short glass fiber reinforced polyamide-66. The developed approach is a modified Mori-Tanaka method that includes coated reinforcements and microscale damage processes. The model takes into account the nonlinear matrix viscoelasticity and the damage mechanisms evolution. The latter is based on the experimental damage investigation previously performed by the authors and presented elsewhere. Damage chronologies have been proposed involving three different local processes: fiber-matrix interface debonding/coating degradation, matrix microcracking and fiber breakage. Each damage mechanism is introduced through an evolution law coupled to local stress fields computed at the microscale. The first numerical results show capability of the developed model to predict the fatigue damage accumulation of the macroscopic homogenized composite material. http://hdl.handle.net/10985/10419 In situ SEM damage mechanisms investigation of short glass fiber reinforced polyamide composite; Investigation in situ des mécanismes d’endommagement dans un composite polyamide renforcé par des fibres courtes ARIF, Muhamad Fatikul; DESPRINGRE, Nicolas; CHEMISKY, Yves; ROBERT, Gilles; MERAGHNI, Fodil Injection molded polyamide composite reinforced with short glass fibers has been widely used in automotive industry due to its high strength to weight ratio and the ability of injection process to produce complex parts. A reliable design of components made of this composite should consider the development of progressive properties degradation due to the damage. A better understanding of the damage mechanisms shall contribute to a better formulation of local damage criteria and thus to include with a higher accuracy the physical modeling of their effects to predict the overall mechanical behavior of the composite. For this purpose, in situ SEM tests were performed to observe the damage mechanisms of injection molded polyamide-66 reinforced with 30%wt of short glass fibers (PA66GF30). The observation was focused on dry as mold state (0% water content) of PA66GF30, which correspond to a relative humidity RH=0%. The specimens were subjected to a flexural load using a three-point bending micro-device and were assembled inside an environmental SEM to allow the in situ observations. Specimens were cut following two specific orientations with respect to the mold flow direction (MFD): longitudinal and transverse. Prior to observation, the surface samples were polished and metalized with gold. As the polyamide absorbs water during polishing, the samples were put after polishing inside a vacuum oven at 80 o C for 15h to ensure that the RH content goes back to zero in the whole sample. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/10419 2013-01-01T00:00:00Z ARIF, Muhamad Fatikul DESPRINGRE, Nicolas CHEMISKY, Yves ROBERT, Gilles MERAGHNI, Fodil Injection molded polyamide composite reinforced with short glass fibers has been widely used in automotive industry due to its high strength to weight ratio and the ability of injection process to produce complex parts. A reliable design of components made of this composite should consider the development of progressive properties degradation due to the damage. A better understanding of the damage mechanisms shall contribute to a better formulation of local damage criteria and thus to include with a higher accuracy the physical modeling of their effects to predict the overall mechanical behavior of the composite. For this purpose, in situ SEM tests were performed to observe the damage mechanisms of injection molded polyamide-66 reinforced with 30%wt of short glass fibers (PA66GF30). The observation was focused on dry as mold state (0% water content) of PA66GF30, which correspond to a relative humidity RH=0%. The specimens were subjected to a flexural load using a three-point bending micro-device and were assembled inside an environmental SEM to allow the in situ observations. Specimens were cut following two specific orientations with respect to the mold flow direction (MFD): longitudinal and transverse. Prior to observation, the surface samples were polished and metalized with gold. As the polyamide absorbs water during polishing, the samples were put after polishing inside a vacuum oven at 80 o C for 15h to ensure that the RH content goes back to zero in the whole sample. http://hdl.handle.net/10985/10268 Micromechanical Fatigue Visco-Damage Model for Short Glass Fiber Reinforced Polyamide-66 DESPRINGRE, Nicolas; CHEMISKY, Yves; ROBERT, Gilles; MERAGHNI, Fodil This work presents a micromechanical fatigue damage model developed for short glass fiber reinforced PA66. It has been developed to predict the high cycle fatigue behavior of PA66/GF30. The model is based on an extended Mori-Tanaka method which includes coated inclusions, matrix viscoelasticity and the evolution of micro-scale damage. The developed model accounts for the nonlinear matrix viscoelasticity and the reinforcement orientation. The description of the damage processes is based on the experimental investigation of damage mechanisms previously performed through in-situ SEM tests and X-ray micro-computed tomography observations. Damage chronologies have been proposed involving three different processes: interface debonding/coating, matrix micro-cracking and fiber breakages. Their occurrence strongly depends on the microstructure and the relative humidity. Each damage mechanism is introduced through an evolution law coupled to local stress fields. The developed model is implemented using a UMAT subroutine. Its experimental validation is achieved under stress or strain controlled fatigue tests. Thu, 01 Jan 2015 00:00:00 GMT http://hdl.handle.net/10985/10268 2015-01-01T00:00:00Z DESPRINGRE, Nicolas CHEMISKY, Yves ROBERT, Gilles MERAGHNI, Fodil This work presents a micromechanical fatigue damage model developed for short glass fiber reinforced PA66. It has been developed to predict the high cycle fatigue behavior of PA66/GF30. The model is based on an extended Mori-Tanaka method which includes coated inclusions, matrix viscoelasticity and the evolution of micro-scale damage. The developed model accounts for the nonlinear matrix viscoelasticity and the reinforcement orientation. The description of the damage processes is based on the experimental investigation of damage mechanisms previously performed through in-situ SEM tests and X-ray micro-computed tomography observations. Damage chronologies have been proposed involving three different processes: interface debonding/coating, matrix micro-cracking and fiber breakages. Their occurrence strongly depends on the microstructure and the relative humidity. Each damage mechanism is introduced through an evolution law coupled to local stress fields. The developed model is implemented using a UMAT subroutine. Its experimental validation is achieved under stress or strain controlled fatigue tests. http://hdl.handle.net/10985/9949 In situ damage mechanisms investigation of PA66/GF30 composite: Effect of relative humidity ARIF, Muhamad Fatikul; MERAGHNI, Fodil; CHEMISKY, Yves; DESPRINGRE, Nicolas; ROBERT, Gilles Damage mechanisms of injection molded polyamide-66/short glass fiber 30 wt% composite (PA66/GF30) were analyzed using in situ SEM mechanical tests on specimens conditioned under three relative humidity contents (RH = 0%, 50% and 100%). The validity of these in situ analyses was confirmed by Xray micro-computed tomography (lCT) observations on tensile loaded specimens. Experimental results demonstrated that relative humidity (RH) conditions influence strongly the damage level and damage mechanisms. Indeed, for specimen with RH = 0%, damage initiation occurs at significantly higher load level than those in RH = 50% and RH = 100% specimens. The higher relative humidity condition also results in higher damage level. Damage chronologies have been proposed as damage initiation in the form of fiber–matrix debonding occurs at fiber ends and more generally at locations where fibers are close to each other due to the generation of local stress concentration (for all studied RH contents), and first fiber breakages occur (RH = 0%). These debonded zones further propagate through fiber–matrix interface (for all studied RH contents), and new fiber breakages develop (RH = 0%). At high relative flexural stress, matrix microcracks appear and grow regardless the RH contents. For RH = 100%, these microcracks are also accompanied by many matrix deformation bands. Subsequently, they lead to the damage accumulation and then to the final failure. Wed, 01 Jan 2014 00:00:00 GMT http://hdl.handle.net/10985/9949 2014-01-01T00:00:00Z ARIF, Muhamad Fatikul MERAGHNI, Fodil CHEMISKY, Yves DESPRINGRE, Nicolas ROBERT, Gilles Damage mechanisms of injection molded polyamide-66/short glass fiber 30 wt% composite (PA66/GF30) were analyzed using in situ SEM mechanical tests on specimens conditioned under three relative humidity contents (RH = 0%, 50% and 100%). The validity of these in situ analyses was confirmed by Xray micro-computed tomography (lCT) observations on tensile loaded specimens. Experimental results demonstrated that relative humidity (RH) conditions influence strongly the damage level and damage mechanisms. Indeed, for specimen with RH = 0%, damage initiation occurs at significantly higher load level than those in RH = 50% and RH = 100% specimens. The higher relative humidity condition also results in higher damage level. Damage chronologies have been proposed as damage initiation in the form of fiber–matrix debonding occurs at fiber ends and more generally at locations where fibers are close to each other due to the generation of local stress concentration (for all studied RH contents), and first fiber breakages occur (RH = 0%). These debonded zones further propagate through fiber–matrix interface (for all studied RH contents), and new fiber breakages develop (RH = 0%). At high relative flexural stress, matrix microcracks appear and grow regardless the RH contents. For RH = 100%, these microcracks are also accompanied by many matrix deformation bands. Subsequently, they lead to the damage accumulation and then to the final failure.