Micromécanique

vignette|Simulation 3D de matériaux soumis aux lois de la micromécanique. La micromécanique est une branche de la mécanique dont l'objectif est de décrire le comportement des matériaux hétérogènes. Les approches micromécaniques consistent généralement à considérer un matériau hétérogène comme un ensemble de constituants dont la morphologie, la répartition et la taille influencent le comportement global. Le terme constituant désigne ainsi un volume discret à l'intérieur duquel les propriétés aussi bien physiques que géométriques sont supposées homogènes et dont la taille définit l'échelle des hétérogénéités prises en compte. Les constituants peuvent être de différents types selon la famille de matériaux considérée : il peut s'agir de la matrice et des renforts dans le cas de matériaux composites ou des cristaux dans le cas de matériaux polycristallins. Une approche micromécanique a généralement un double objectif : être capable de déterminer l'état mécanique (i.e. contrainte et déform

Elimination of ringing artifacts by finite-element projection in FFT-based homogenization

Ali Falsafi, Till Junge

Micromechanical homogenization is often carried out with Fourier-accelerated methods that are prone to ringing artifacts. We here generalize the compatibility projection introduced by Vond.rejc et al. (2014) [24] beyond the Fourier basis. In particular, we formulate the compatibility projection for linear finite elements while maintaining Fourier-acceleration and the fast convergence properties of the original method. We demonstrate that this eliminates ringing artifacts and yields an efficient computational homogenization scheme that is equivalent to canonical finite-element formulations on fully structured grids. (C) 2021 The Author(s). Published by Elsevier Inc.

ACADEMIC PRESS INC ELSEVIER SCIENCE2022

Static and dynamic mechanical properties of nanosilica and multiwalled carbon nanotube reinforced acrylonitrile butadiene styrene composites: theoretical mechanism of nanofiller reinforcement

Thomas Keller, Harish Mohan Thettemmel

Experimental and theoretical approaches were employed to analyze the static and dynamic mechanical properties of acrylonitrile butadiene styrene (ABS) nanocomposites reinforced with multiwalled carbon nanotube (MWCNT) and nanosilica. Enhanced stiffness and tensile strength were observed for composites with 5% (wt) CNT and 3% (wt) nanosilica. Micromechanical models were highly promising to predict the experimental Young's modulus by 2% (wt) of nanofiller content, beyond which it deviated due to the nanofiller population and the reduction in interparticle distance. At the optimum content of 5% (wt) MWCNTs in the ABS matrix, enhanced storage and loss moduli and lowered damping peak were observed, which was attributed to the immobilization of the segmental polymer chains. From the DMA parameters, the dynamics of the polymer chain were investigated and the fraction of constrained regions and entanglement density were quantified. These findings demonstrated that composite with higher constrained regions and entanglements exhibited superior mechanical performance. Amongst all composites, 5% (wt) MWCNT-reinforced ABS composite showed an increment in reinforcing efficiency, entanglement density, and constrained regions by 195.6%, 115% and 55.5%, respectively, with regard to 3% (wt) nanosilica-reinforced ABS composite. The effectiveness of dispersion and interfacial adhesion of CNTs with ABS was improved by carboxyl treatment and functionalization with ABS-g-MaH compatibilizer with regard to silane-treated nanosilica/ABS composites. Combined analysis of microstructure, tensile properties and dynamic mechanical parameters such as entanglement density, effectiveness of filler, constrained volume of polymer chains and adhesion factor demonstrated the effectiveness of high aspect ratio carboxyl-treated MWCNTs as a better reinforcing agent in comparison with nanosilica in ABS matrix.

SPRINGER2021

Static and dynamic mechanical properties of nanosilica and multiwalled carbon nanotube reinforced acrylonitrile butadiene styrene composites: theoretical mechanism of nanofiller reinforcement

Thomas Keller, Harish Mohan Thettemmel

SPRINGER2021

Development and application of a micromechanics-based numerical approach for the study of crack propagation in concrete

Elimination of ringing artifacts by finite-element projection in FFT-based homogenization

Static and dynamic mechanical properties of nanosilica and multiwalled carbon nanotube reinforced acrylonitrile butadiene styrene composites: theoretical mechanism of nanofiller reinforcement

Elimination of ringing artifacts by finite-element projection in FFT-based homogenization

Development and application of a micromechanics-based numerical approach for the study of crack propagation in concrete

Static and dynamic mechanical properties of nanosilica and multiwalled carbon nanotube reinforced acrylonitrile butadiene styrene composites: theoretical mechanism of nanofiller reinforcement