|Tensile strength of granular aggregates: Stress chains across particle phase versus stress concentration by pores |
(Article) Publié: Physical Review E, vol. 102 p.022906 (2020)
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We use the bond-based peridynamics approach to analyze the strength and fracture of dense granularaggregates with variable amount of a solid binding matrix, distributed according to a simple protocol in theinterstitial space between particles. We show the versatility of the peridynamics approach in application to crackpropagation and its scaling behavior in a homogeneous medium (in the absence of particles and pores). Thenwe apply this method to simulate the deformation and failure of aggregates as a function of the amount of thebinding matrix under tensile loading. We find that the tensile strength is a strongly nonlinear function of thematrix volume fraction. It first increases slowly and levels off as the gap space in-between touching particles isgradually filled by the binding matrix, up to nearly 90% of the total pore volume, and then a rapid increase occursto the maximum strength as the remaining interstitial space, composed of isolated pores between four or moreparticles, is filled. By analyzing the probability density functions of stresses in the particle and matrix phases, weshow that the adhesion of the matrix to the particles and the thickening of stress chains (i.e., stresses distributedover larger cross sections) control the strength in the first case whereas the homogenizing effect of the matrixby filling the pores (hence reducing stress concentration) is at the origin of further increase of the strength in thesecond case. Interestingly, these two mechanisms contribute almost equally to the total strength.