Representative volume elements for the simulation of isotropic composites highly filled with monosized spheres

Strauch-Hausser

2021

Soft Matter

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Section: Micromechanics Analysis 41 Modelsmentioning

confidence: 96%

Linear viscoelasticity of an acrylate IPN, analysis and micromechanical modeling

Strauch-Hausser

2021

Soft Matter

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“…Since no damage has occurred yet at infinitesimal strain, knowing the linear elastic behavior of the fillers and the matrix, a simple option is to use a mean field micromechanics model to estimate the Young moduli of the composites. It has been shown in (Ghossein and Lévesque, 2012;Gusev, 2016;de Francqueville et al, 2019) that the generalized self-consistent (GSC) model (Christensen and Lo, 1979;Christensen, 1990) defined for spherical particles, provides with the same results as a finite elements numerical homogenization approach. The Young modulus of the matrix filled with 20% of aluminium powder is estimated to 0.57 MPa with the GSC model using the standard aluminium properties E = 69 GPa and ν = 0.346 (Ashby, 1981).…”

Section: Linear Behaviormentioning

confidence: 99%

“…In order to build similar microstructures with non-regular polyhedral particles (Fig. 7b), the centers of the spheres of an isotropic microstructure (de Francqueville et al, 2019) are used as seed points for a Voronoï diagram. The obtained polyhedra are shrinked to obtain particles of the same volumes and the targeted overall volume fraction.…”

Section: Linear Behaviormentioning

confidence: 99%

“…Note that at 55% volume fraction of fillers, it is not obvious to generate microstructures with well dispersed particles and a relatively large number of microstructures presenting some kind of order have been discarded. During this process, two microstructures stood out, presenting a rather good isotropy with questionable randomness when evaluating the nearest neighbor distribution function (de Francqueville et al, 2019). Actually, particle percolation paths or particle clustering were suspected.…”

Section: Linear Behaviormentioning

confidence: 99%

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Use of a micromechanical approach to understand the mechanical behavior of solid propellants

Francqueville

Pierre

et al. 2021

Mechanics of Materials

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The development of new generations of propellants with better energetic properties may be hampered by unsatisfactory mechanical behaviors in terms of strength and toughness. A micromechanical approach is adopted to provide a better understanding of the existing links between the constitutive phase behaviors and the local damage, and the macroscopic mechanical behavior of these materials. Three model materials have been made and tested in uniaxial tension. The stress-strain responses were recorded while monitoring their volume changes that quantify the macroscopic damage. A qualitative description of the local damage was obtained thanks to scanning electron microscopy images of samples under loading. The micromechanical approach consists in finite elements analyses on periodic microstructures of non-regular polyhedral particles embedded in a soft matrix. An original microstructure generation tool has been developed specifically in order to obtain highly filled isotropic microstructures. Debonding at the matrix/filler interface was taken into account with a cohesive-zone model (CZM). The impact of the CZM parameters is discussed, in an effort to make the link between the CZM parameters and how the local damage appears and develops, and between the cohesive behavior and the shape of the macroscopic stress-stretch responses of the heterogeneous materials.

“…XR-μCT imaging in the initial state (a) and at 5% (b), 10% (c), and 15% (d) uniaxial tensile strain. (de Francqueville et al, 2019). Finite element analyses have been carried out using Abaqus (2018) finite element code, for is its proven ability to cope with large strain and with interface debonding through cohesive-zone models (Park and Paulino, 2011).…”

Section: Microstructure Generation and Numerical Frameworkmentioning

confidence: 99%

Relationship between local damage and macroscopic response of soft materials highly reinforced by monodispersed particles

Francqueville

Pierre

et al. 2020

Mechanics of Materials

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A rubberlike matrix highly filled with spherical micrometric glass beads is submitted to uniaxial tension tests until break. X-ray tomography imaging performed on the material while submitted to uniaxial tension reveals early debonding at the matrix/filler interfaces at the poles of the particles followed by void coalescence creating damage localization. The latter causes a downturn of the macroscopic stress-strain response. These phenomena are analyzed further with three-dimensional finite element simulations, where 64 spherical beads are distributed randomly in a periodic cell. A simple version of the Tvergaard-Hutchinson cohesive-zone model allows to reproduce all the experimental trends well. The effects of the three parameters involved are analyzed, and three different types of macroscopic behaviors are observed corresponding to three different microstructure damages. The value of the initial stiffness of the interface, limited by numerical convergence, has little effect on how the local damage evolves but has a significant impact on the overall macroscopic stress values. The local damage is strongly dependent on the critical strength and the separation failure displacement, and the adhesion energy may be considered as a resulting parameter of the two previous ones. The interfacial critical strength appears to have a significant impact on the damage initiation, either spread across the structure for low values, or localized for high values. Increasing the interface separation failure displacement delays the possible loss of adhesion to a higher strain and preserves the integrity of the composite material.