1,721,028 research outputs found
GRAPHENE-BASED COMPOSITE MATERIALS FOR AUTOMOTIVES
Full text linkThe present initiative provides a summary overview on Graphene Related materials (GRM) for automotive applications and investigates efficient ways to integrate Graphene as polymer reinforcements within composite materials for energy-efficient and safe vehicles (EESVs). An approach that starts from the nano-scale through the Graphene elaboration by experiments to meso/macro-scale by continuum mechanics modelling is discussed with respect to some limiting factors in terms of the large scale production, the interfacial behaviour, the amount of wrinkling and network structure. Finally, a strategy for modelling such a composite is elaborated in the framework of the Graphene Flagship to well understand such limitations for a full applicability of Graphene. It is anticipated that this initiative will advance innovative lightweight graphene composites and their related modelling, designing, manufacturing, and joining capabilities suitable for automotive industry which requires unique levels of affordability, mechanical performance, green environmental impact and energy efficiency. This leads to complete understanding of the new graphene composites and their applicability in high-volume production scenario
Micromechanics Modelling of Graphene Platelets Reinforced Polymer Composite Materials With Imperfect Interfaces
Full text linkCrashworthiness modelling of hierarchical short glass fibres reinforced graphene polymer composites materials
Full text linkThis work aims to analyse the response under crashworthiness impact of an automotive crash box composite consisting on short glass fibres that are embedded within graphene reinforced polymer composite. Analytical as well as finite element techniques are employed to derive the overall composite response and mechanical characterisation for a macroscopic structural crashworthiness application. Graphene sheets are considered as platelets GPL embedded within an elasto plastic polymer matrix phase leading to a 2-phases graphene/polymer composite. The modelling of 3-phases short glass fibres/graphene polymer composite consists on a double-scale approach combining the 2-phases graphene polymer composite as matrix phase in which are embedded the glass fibres. The full structure crash box is simulated at each Gauss integration point by implementing the constitutive 3-phases composite using a user-defined materials subroutine
Conception et amélioration des propriétés amortissantes des composites auxétiques basés sur l'utilisation des outils de la micromécanique
No full textThe design of composite (particles/fibers or structures) materials, consisting of auxetic reinforcements, with enhanced damping properties is studied herein. For such analysis, the auxetic behavior describing a negative Poisson's ratio needs to be understood as "structure effect" point of view than "material effect". Indeed, the "material effect" which treats of the topological and morphological textures of the composite constituents remains poorly documented in the literature. Based on the kinematic integral equation of Dederichs and Zeller, the design space of auxetic composite materials is explored initially through an analytical one-site formulation of the Mori-Tanaka micromechanics scheme. Then, more complex microstructures are investigated from micromechanics formalism as well as Finite Element Method (FEM) simulations. One can cite the multilayered hollow-cored microstructure and the microstructure describing a cluster of re-entrant ellipsoidal inclusions in which the interaction among them (inclusions) is taken into account. The results provided by these investigations show us for instance in the case of isotropic materials that auxeticity is achieved if and only if one of the material?s constituents (inclusion or matrix) is initially auxetic. Also, it is noticed in the case of ellipsoidal inclusions describing the re-entrant cluster that auxetic behavior can be recovered by introducing joints between inclusions. Otherwise, favorable issues are only expected with auxetic components. In addition to this preliminary analysis concerning the validity domain of auxetic behavior in composites, the effect of inserting auxetic reinforcements within a viscoelastic matrix for instance PolyVinylButyral (PVB) on the one hand, and the use of auxetic and viscoelastic layers in sandwich structures on the other hand, are studied. The response of these materials in terms of damping properties, such as the storage modulus and the loss factor are then identified and discussed versus non-auxetic (conventional) composite reinforcementsLa conception de matériaux composites à particules, fibres ou structures sandwichs, faits de renforts auxétiques en vue de l'amélioration des propriétés amortissantes, est analysée dans cette thèse. Pour une telle analyse, le comportement auxétique décrivant un coefficient de Poisson négatif nécessite d'être compris tant d'un point de vue « effet structure » que « effet matériau ». Ce dernier point c'est-à-dire l'« effet matériau », faisant référence à la forme, aux orientations et différentes propriétés des phases constitutives du matériau, reste peu documenté dans la littérature scientifique. Ainsi partant d'un formalisme micromécanique basé sur l'équation cinématique intégrale de Dederichs et Zeller, nous explorons dans un premier temps et analytiquement le domaine de validité du matériau composite auxétique par le schéma mono-site de Mori-Tanaka. Ensuite des microstructures plus complexes, à l'instar de la microstructure du vide multi-enrobé et celle d'un cluster réentrant d'inclusions ellipsoïdales prenant en compte les interactions de ces dernières, sont étudiées et validées par des simulations Eléments Finis. Les résultats de ces analyses nous indiquent, par ailleurs dans le cas des matériaux isotropes que le comportement auxétique n'est atteint que si et seulement si une des phases du composite est initialement auxétique. Aussi, la nécessité d'introduire des liaisons ou inter-connections au niveau des inclusions ellipsoïdales est montrée comme étant la méthode conduisant à un effet auxétique au niveau de la microstructure du cluster réentrant. Outre cette analyse préliminaire sur le domaine de validité du comportement auxétique dans les composites, l'effet de l'introduction d'inclusions auxétiques dans une matrice viscoélastique en l'occurrence le PolyVinyle de Butyral (PVB) d'une part et l'utilisation de couches viscoélastiques et auxétiques dans les structures sandwichs d'autre part, ont été étudiés. Les réponses de ces matériaux en termes de propriétés amortissantes, telles que le module de stockage et le facteur de perte, sont alors déterminées et discutées par rapport aux composites à renforts non auxétiques (conventionnels
Nonlinear Elastic Moduli of Graphene Sheet-Reinforced Polymer Composites for Automotive Applications
No full textThe non-linear elastic moduli of the Graphene sheet-reinforced polymer composite are investigated using a combined molecular mechanics theory and continuum homogenisation tools. Under uni-axial loading, the linear and non-linear constitutive equations of the Graphene sheet are derived from a Taylor series expansion in powers of strains. Based on the modified Morse potential, the elastic moduli and Poisson’s ratio are obtained for the Graphene sheet leading to the derivation of the non-linear stiffness tensor. For homogenisation purpose, the strain concentration tensor is computed by the means of the irreducible decomposition of the Eshelby’s tensor for an arbitrary domain. Therefore, a mathematical expression of the averaged Eshelby’s tensor for a rectangular shape is obtained for the Graphene sheet. Under the Mori–Tanaka micro-mechanics scheme, the effective non-linear behaviour is predicted for various micro-parameters such as the aspect ratio and mass fractions. Numerical results highlight the effect of such micro-parameters on the anisotropic degree of the composite
Constitutive modelling of ductile damage matrix reinforced by platelets-like particles with imperfect interfaces: Application to graphene polymer nanocomposite materials
Full text linkIn this paper, the mechanical response of composites consisting of ductile matrix reinforced by platelets-like particles is derived with imperfect interfaces. Due to its flexibility to study imperfect interfaces with limited number of model parameters, the linear spring model LSM is considered. Moreover, the interfacial contribution to the strain concentration tensor within each material phase and inside the average strain filed is described by a modified Mori-Tanaka scheme. The material nonlinearity is established by the J2 plasticity and Lemaitre-Chaboche damage model. A generalised mid-point rule is used to solve rate equations yielding to anisotropic consistent (algorithmic) tangent operators. To avoid spurious macroscopic stress-strain response, an isotropisation procedure is adopted during the computation of a modified Eshelby's tensor. Numerical results are performed on graphene platelets GPL-reinforced polymer PA6 composite. They confirm the possibility to achieve high stiffness with low values of GPL aspect ratio. The accumulated plastic strain and the damage variable within the matrix are influenced by the GPL volume fraction which is also involved in the softening of the overall response when imperfection is considered at the interface
Multiscale modelling of the mechanical behaviour of bio-based composite materials
No full textInternational audienceNatural fibre reinforced polymer composite materials have gained a lot of interest due to lightweighting, recyclability, and environmental reasons [1]. Indeed, bio-fibres such as hemp, wood, basalt, rice husk, coir, sisal, ramie, flax, kenaf, jute, etc., have attracted significant focus as a potential alternative to synthetic fibres like carbon and glass [2]. Design parameters, mainly the aspect ratio and volume fraction, as well as the orientation of the fibres can influence the effective behaviour of the composite. It depends on the properties of the fibres and the matrix, which can exhibit material nonlinearity. The polymer matrix usually undergoes rate-(in)dependent behaviour, which may lead to a damage initiation. Therefore, a predictive model has become a relevant tool that helps study composite materials without expensive test campaigns.In this work, a micromechanics modelling combining rate-dependant (elasto-visco-plastic) constitutive laws and multi-site interactions of inclusions has been developed for studying the nonlinear response of bio-based composite materials. The multi-site interaction results in the accounting for material anisotropy. It considers the interaction of inclusions with a considered neighbourhood. For each material phase, a consistent tangent modulus is obtained and serves as a uniform modulus for homogenisation. The Generalized Mori–Tanaka (GMT) scheme derives the effective properties of the composite. To avoid numericalinstabilities when time increments become very small, a regulation procedure for the visco- plastic function is adopted in the computation of the consistent tangent modulus [3]. The developed constitutive laws are implemented as a user-material UMAT in a Finite Element code as shown in Figure 1. An application is done on automotive inner door handles using flax fibre reinforced polycarbonate composite materials
Crashworthiness modelling of hierarchical short glass fibres reinforced graphene polymer composites materials
No full textInternational audienc
Multi scale modelling of graphene platelets reinforced polymer matrix composite materials
Full text linkDesign concepts and methods for high damping/dynamic properties of auxetic reinforced multifunctional materials
No full textLa conception de matériaux composites à particules, fibres ou structures sandwichs, faits de renforts auxétiques en vue de l'amélioration des propriétés amortissantes, est analysée dans cette thèse. Pour une telle analyse, le comportement auxétique décrivant un coefficient de Poisson négatif nécessite d'être compris tant d'un point de vue « effet structure » que « effet matériau ». Ce dernier point c'est-à-dire l'« effet matériau », faisant référence à la forme, aux orientations et différentes propriétés des phases constitutives du matériau, reste peu documenté dans la littérature scientifique. Ainsi partant d'un formalisme micromécanique basé sur l'équation cinématique intégrale de Dederichs et Zeller, nous explorons dans un premier temps et analytiquement le domaine de validité du matériau composite auxétique par le schéma mono-site de Mori-Tanaka. Ensuite des microstructures plus complexes, à l'instar de la microstructure du vide multi-enrobé et celle d'un cluster réentrant d'inclusions ellipsoïdales prenant en compte les interactions de ces dernières, sont étudiées et validées par des simulations Eléments Finis. Les résultats de ces analyses nous indiquent, par ailleurs dans le cas des matériaux isotropes que le comportement auxétique n'est atteint que si et seulement si une des phases du composite est initialement auxétique. Aussi, la nécessité d'introduire des liaisons ou inter-connections au niveau des inclusions ellipsoïdales est montrée comme étant la méthode conduisant à un effet auxétique au niveau de la microstructure du cluster réentrant. Outre cette analyse préliminaire sur le domaine de validité du comportement auxétique dans les composites, l'effet de l'introduction d'inclusions auxétiques dans une matrice viscoélastique en l'occurrence le PolyVinyle de Butyral (PVB) d'une part et l'utilisation de couches viscoélastiques et auxétiques dans les structures sandwichs d'autre part, ont été étudiés. Les réponses de ces matériaux en termes de propriétés amortissantes, telles que le module de stockage et le facteur de perte, sont alors déterminées et discutées par rapport aux composites à renforts non auxétiques (conventionnels)The design of composite (particles/fibers or structures) materials, consisting of auxetic reinforcements, with enhanced damping properties is studied herein. For such analysis, the auxetic behavior describing a negative Poisson's ratio needs to be understood as "structure effect" point of view than "material effect". Indeed, the "material effect" which treats of the topological and morphological textures of the composite constituents remains poorly documented in the literature. Based on the kinematic integral equation of Dederichs and Zeller, the design space of auxetic composite materials is explored initially through an analytical one-site formulation of the Mori-Tanaka micromechanics scheme. Then, more complex microstructures are investigated from micromechanics formalism as well as Finite Element Method (FEM) simulations. One can cite the multilayered hollow-cored microstructure and the microstructure describing a cluster of re-entrant ellipsoidal inclusions in which the interaction among them (inclusions) is taken into account. The results provided by these investigations show us for instance in the case of isotropic materials that auxeticity is achieved if and only if one of the material?s constituents (inclusion or matrix) is initially auxetic. Also, it is noticed in the case of ellipsoidal inclusions describing the re-entrant cluster that auxetic behavior can be recovered by introducing joints between inclusions. Otherwise, favorable issues are only expected with auxetic components. In addition to this preliminary analysis concerning the validity domain of auxetic behavior in composites, the effect of inserting auxetic reinforcements within a viscoelastic matrix for instance PolyVinylButyral (PVB) on the one hand, and the use of auxetic and viscoelastic layers in sandwich structures on the other hand, are studied. The response of these materials in terms of damping properties, such as the storage modulus and the loss factor are then identified and discussed versus non-auxetic (conventional) composite reinforcement
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