Microstructural controls of anticrack nucleation in highly porous brittle solids

Jonas Ritter,Henning Löwe,Johan Gaume

doi:10.1038/s41598-020-67926-2

Jonas Ritter, Henning Löwe + Show 1 more

Open Access

https://doi.org/10.1038/s41598-020-67926-2

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Abstract

Porous brittle solids have the ability to collapse and fail even under compressive stresses. In fracture mechanics, this singular behavior, often referred to as anticrack, demands for appropriate continuum models to predict the catastrophic failure. To identify universal controls of anticracks, we link the microstructure of a porous solid with its yield surface at the onset of plastic flow. We utilize an assembly method for porous structures, which allows to independently vary microstructural properties (density and coordination number) and perform discrete element simulations under mixed-mode (shear-compression) loading. In rescaled stress coordinates, the concurrent influence of the microstructural properties can be cast into a universal, ellipsoidal form of the yield surface that reveals an associative plastic flow rule, as a common feature of these materials. Our results constitute a constructive approach for continuum modeling of anticrack nucleation and propagation in highly porous brittle, engineering and geo-materials.

Highlights

Large-strain, dynamic simulations for a comprehensive ensemble of different microstructures are still elaborate, which impedes the understanding of universal microstructural drivers of the complex mechanical behavior involved in anticracks
Increasing values of volume fractions and/or increasing values of coordination number lead to increasing elastic modulus and compressive strength
An explanation as to why the yield surface is predominantly controlled by volume fraction and contact density is suggested by the fact that for arbitrary particle-based two-phase systems, the link between physical and structural properties is completely embodied in the hierarchy of n−point correlation functions[33]

Summary

Introduction

Large-strain, dynamic simulations for a comprehensive ensemble of different microstructures are still elaborate, which impedes the understanding of universal microstructural drivers of the complex mechanical behavior involved in anticracks. Rather a significant variation of the (mechanically) relevant parameters, i.e. volume fraction and the coordination number, are required to understand the controls of porosity and matrix connectivity on anticracks. A mapping of particle properties to continuous two-phase microstructures acquired by XRCT is principally feasible in the sense of a stochastic reconstruction, by matching two-point correlation functions[31]. We employ this methodology to systematically investigate a large ensemble of diverse microstructures with a wide range of coordination numbers and volume fractions within DEM under mixed-mode loading conditions (Fig. 1). The results provide fundamental insight how the continuum mechanical behaviour of very loose and brittle solids is controlled by volume fraction and microstructural connectivity

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