G. Régnier - Academia.edu (original) (raw)
Papers by G. Régnier
Microelectronic Engineering, 2013
ABSTRACT: The accurate prediction of both the elastic properties and the thermal expansion coeffi... more ABSTRACT: The accurate prediction of both the elastic properties and the thermal expansion coefficien very important for the precise simulation of such processes as injection molding of short-fiber polymer-m composites. In this work, a two-step homogenization procedure is applied and compared with experim values obtained on a polyarylamide/glass fiber composite for a broad range of temperatures. It is obse that the stiffness averaging version of the model surpasses the compliance averaging variant, especially w it is combined with a precise evaluation of the fourth-order orientation tensor. It is also demonstrated tha orthotropic closure approximations are significantly better than previous ones (linear, quadratic, and hy and than a very recent one. Among the orthotropic closure approximations, the fitted ones lead to accep results, which are very close to those obtained with the experimentally measured fourth-order orient tensor
Isothermal crystallizations of a poly(etherketoneketone) (PEKK) copolymer matrix prepared from di... more Isothermal crystallizations of a poly(etherketoneketone) (PEKK) copolymer matrix prepared from diphenyl ether (DPE), terephthalic acid (T) and isophthalic acid (I) has been investigated by differential scanning calorimetry. Crystallization kinetics have been modeled by using a two stage modified Avrami model which takes into the complex crystallization of PEKK matrix. The influence of carbon fibers on PEKK crystallization kinetics has also been investigated for PEKK prepreg tapes. Based on those modelling, Time-Temperature-Transformation (TTT) diagrams of the crystallization of both neat resin and prepregs have been established providing an indispensable tool for PEKK composite processing. Finally, mechanical properties of neat PEKK resin samples having undergone different heat treatments have been measured to draw conclusions as the influence of crystallinity on final mechanical performances.
Carbon nanotubes (CNT) are very long cylinders formed by rolled-up graphene sheets at the nano sc... more Carbon nanotubes (CNT) are very long cylinders formed by rolled-up graphene sheets at the nano scale. In addition to their unique structure, interest for CNTs is based on their impressive physical properties [1]. CNTs have been envisaged as component-material in a large range of applications: electrical circuits, nano-probes for near-field microscopes, high-resolution gas-molecules detectors, drug and gene delivery systems, highstrength fibres and high-performance polymer-based composites. A large number of envisaged applications require dissolving CNTs and processing them in liquid phase. Control of those forming processes needs a deep understanding of the rheology of CNT suspensions [2]. In that context, this work tackles the modelling of the rheological behaviour of dilute and low semi-dilute suspensions of treated CNTs into a Newtonian solvent. CNTs have an important influence on the viscous behaviour of their suspensions. For example, dilute and low semi-dilute suspensions of t...
Polymer Degradation and Stability
International Journal of Material Forming
Polymer Degradation and Stability
Abstract This paper reports the hydrolysis of several PBT materials (pigmented or not). Degradati... more Abstract This paper reports the hydrolysis of several PBT materials (pigmented or not). Degradation was monitored by gel permeation chromatography (chain scission), DSC (crystalline morphology), tensile test (residual mechanical properties) and DVS (polymer-water interaction). The embrittlement comes from chain scission associated with a small chemicrystallization effect. Results lead to the proposal of a kinetic model for the chain scission rate aimed to describe the auto-acceleration effect induced by carboxylic acids (chain ends) and successfully compared to results both from this work or literature. The mixed “average molar mass – crystallinity” criterion proposed in a previous paper was specified. At last, the effect of pigments is illustrated and shows that carbon black (present in particular in one masterbatch) plays an aggravating role on hydrolysis.
Polymer Degradation and Stability
AIP Conference Proceedings
AIP Conference Proceedings, 2016
Isothermal melt and cold crystallization kinetics of poly(etherketoneketone) (PEKK) have been inv... more Isothermal melt and cold crystallization kinetics of poly(etherketoneketone) (PEKK) have been investigated by differential scanning calorimetry. A modified Avrami model has been used to describe the two-stage crystallization of PEKK. The primary crystallization stage is assumed to be a two dimensional nucleation growth with an Avrami exponent of 2 whereas the secondary stage is assumed to be a one dimensional nucleation growth with an Avrami exponent of 1. The evolution of the crystallization constant rates depending on temperature has been modeled with the Hoffman and Lauritzen growth equation. The activation energy of nucleation constants Kg for both crystallizations are presented.
International Journal of Material Forming, 2008
La realisation des moules pour l'injection des thermoplastiques demande un gros investissemen... more La realisation des moules pour l'injection des thermoplastiques demande un gros investissement financier ; en consequence, les industriels souhaitent parvenir a predire correctement la geometrie finale des pieces injectees. Pour cela, un calcul rheologique couple a un calcul thermo-mecanique par elements finis dans le solide doit etre mene et requiert les proprietes du materiau. Aujourd'hui, les proprietes mecaniques des materiaux utilisees dans les codes de calcul ne sont generalement ni thermo-dependantes, ni directement dependantes de l'orientation locale des fibres. L'objectif de cette etude est de parvenir a predire les proprietes elastiques et les coefficients de dilatation de composites injectes et charges de fibres courtes, en ayant recours a des techniques d'homogeneisation. L'originalite du travail reside dans le fait d'estimer ces proprietes sur une large gamme de temperature en fonction de l'orientation locale des fibres. Une 1ere partie presente les techniques de mesure de l'etat d'orientation des fibres : dans le cas particulier de l'injection ou la plupart des fibres sont contenues dans un plan, nous avons mis au point une nouvelle methode rapide et precise afin de determiner l'orientation spatiale des fibres. Elle consiste a analyser l'image, prise au microscope electronique a balayage, d'un seul plan de coupe incline par rapport a la direction d'injection. Dans une 2eme partie, les proprietes thermo-elastiques des composites sont obtenues par le modele de Mori-Tanaka. Pour tenir compte de l'orientation, plusieurs methodologies sont evaluees. Finalement, nous proposons d'utiliser une fonction capable de decrire la forme de la distribution d'orientation et dont les parametres sont identifies a partir du tenseur d'orientation d'ordre 2. Les predictions obtenues sont coherentes avec les mesures de modules d'Young et de coefficients de dilatation.
International Journal of Forming Processes, 2003
International Journal of Forming Processes, 2003
Microelectronic Engineering, 2013
ABSTRACT: The accurate prediction of both the elastic properties and the thermal expansion coeffi... more ABSTRACT: The accurate prediction of both the elastic properties and the thermal expansion coefficien very important for the precise simulation of such processes as injection molding of short-fiber polymer-m composites. In this work, a two-step homogenization procedure is applied and compared with experim values obtained on a polyarylamide/glass fiber composite for a broad range of temperatures. It is obse that the stiffness averaging version of the model surpasses the compliance averaging variant, especially w it is combined with a precise evaluation of the fourth-order orientation tensor. It is also demonstrated tha orthotropic closure approximations are significantly better than previous ones (linear, quadratic, and hy and than a very recent one. Among the orthotropic closure approximations, the fitted ones lead to accep results, which are very close to those obtained with the experimentally measured fourth-order orient tensor
Isothermal crystallizations of a poly(etherketoneketone) (PEKK) copolymer matrix prepared from di... more Isothermal crystallizations of a poly(etherketoneketone) (PEKK) copolymer matrix prepared from diphenyl ether (DPE), terephthalic acid (T) and isophthalic acid (I) has been investigated by differential scanning calorimetry. Crystallization kinetics have been modeled by using a two stage modified Avrami model which takes into the complex crystallization of PEKK matrix. The influence of carbon fibers on PEKK crystallization kinetics has also been investigated for PEKK prepreg tapes. Based on those modelling, Time-Temperature-Transformation (TTT) diagrams of the crystallization of both neat resin and prepregs have been established providing an indispensable tool for PEKK composite processing. Finally, mechanical properties of neat PEKK resin samples having undergone different heat treatments have been measured to draw conclusions as the influence of crystallinity on final mechanical performances.
Carbon nanotubes (CNT) are very long cylinders formed by rolled-up graphene sheets at the nano sc... more Carbon nanotubes (CNT) are very long cylinders formed by rolled-up graphene sheets at the nano scale. In addition to their unique structure, interest for CNTs is based on their impressive physical properties [1]. CNTs have been envisaged as component-material in a large range of applications: electrical circuits, nano-probes for near-field microscopes, high-resolution gas-molecules detectors, drug and gene delivery systems, highstrength fibres and high-performance polymer-based composites. A large number of envisaged applications require dissolving CNTs and processing them in liquid phase. Control of those forming processes needs a deep understanding of the rheology of CNT suspensions [2]. In that context, this work tackles the modelling of the rheological behaviour of dilute and low semi-dilute suspensions of treated CNTs into a Newtonian solvent. CNTs have an important influence on the viscous behaviour of their suspensions. For example, dilute and low semi-dilute suspensions of t...
Polymer Degradation and Stability
International Journal of Material Forming
Polymer Degradation and Stability
Abstract This paper reports the hydrolysis of several PBT materials (pigmented or not). Degradati... more Abstract This paper reports the hydrolysis of several PBT materials (pigmented or not). Degradation was monitored by gel permeation chromatography (chain scission), DSC (crystalline morphology), tensile test (residual mechanical properties) and DVS (polymer-water interaction). The embrittlement comes from chain scission associated with a small chemicrystallization effect. Results lead to the proposal of a kinetic model for the chain scission rate aimed to describe the auto-acceleration effect induced by carboxylic acids (chain ends) and successfully compared to results both from this work or literature. The mixed “average molar mass – crystallinity” criterion proposed in a previous paper was specified. At last, the effect of pigments is illustrated and shows that carbon black (present in particular in one masterbatch) plays an aggravating role on hydrolysis.
Polymer Degradation and Stability
AIP Conference Proceedings
AIP Conference Proceedings, 2016
Isothermal melt and cold crystallization kinetics of poly(etherketoneketone) (PEKK) have been inv... more Isothermal melt and cold crystallization kinetics of poly(etherketoneketone) (PEKK) have been investigated by differential scanning calorimetry. A modified Avrami model has been used to describe the two-stage crystallization of PEKK. The primary crystallization stage is assumed to be a two dimensional nucleation growth with an Avrami exponent of 2 whereas the secondary stage is assumed to be a one dimensional nucleation growth with an Avrami exponent of 1. The evolution of the crystallization constant rates depending on temperature has been modeled with the Hoffman and Lauritzen growth equation. The activation energy of nucleation constants Kg for both crystallizations are presented.
International Journal of Material Forming, 2008
La realisation des moules pour l'injection des thermoplastiques demande un gros investissemen... more La realisation des moules pour l'injection des thermoplastiques demande un gros investissement financier ; en consequence, les industriels souhaitent parvenir a predire correctement la geometrie finale des pieces injectees. Pour cela, un calcul rheologique couple a un calcul thermo-mecanique par elements finis dans le solide doit etre mene et requiert les proprietes du materiau. Aujourd'hui, les proprietes mecaniques des materiaux utilisees dans les codes de calcul ne sont generalement ni thermo-dependantes, ni directement dependantes de l'orientation locale des fibres. L'objectif de cette etude est de parvenir a predire les proprietes elastiques et les coefficients de dilatation de composites injectes et charges de fibres courtes, en ayant recours a des techniques d'homogeneisation. L'originalite du travail reside dans le fait d'estimer ces proprietes sur une large gamme de temperature en fonction de l'orientation locale des fibres. Une 1ere partie presente les techniques de mesure de l'etat d'orientation des fibres : dans le cas particulier de l'injection ou la plupart des fibres sont contenues dans un plan, nous avons mis au point une nouvelle methode rapide et precise afin de determiner l'orientation spatiale des fibres. Elle consiste a analyser l'image, prise au microscope electronique a balayage, d'un seul plan de coupe incline par rapport a la direction d'injection. Dans une 2eme partie, les proprietes thermo-elastiques des composites sont obtenues par le modele de Mori-Tanaka. Pour tenir compte de l'orientation, plusieurs methodologies sont evaluees. Finalement, nous proposons d'utiliser une fonction capable de decrire la forme de la distribution d'orientation et dont les parametres sont identifies a partir du tenseur d'orientation d'ordre 2. Les predictions obtenues sont coherentes avec les mesures de modules d'Young et de coefficients de dilatation.
International Journal of Forming Processes, 2003
International Journal of Forming Processes, 2003