Abstract
The mechanical properties of a disordered heterogeneous medium depend, in general, on a complex interplay between multiple length scales. Connecting local interactions to macroscopic observables, such as stiffness or fracture, is thus challenging in this type of material. Here, we study the properties of a cohesive granular material composed of glass beads held together by soft polymer bridges. We characterise the mechanical response of single bridges under traction and shear, using a setup based on the deflection of flexible micropipettes. These measurements, along with information from X-ray microtomograms of the granular packings, then inform large-scale discrete element model (DEM) simulations. Although simple, these simulations are constrained in every way by empirical measurement and accurately predict mechanical responses of the aggregates, including details on their compressive failure, and how the material's stiffness depends on the stiffness and geometry of its parts. By demonstrating how to accurately relate microscopic information to macroscopic properties, these results provide new perspectives for predicting the behaviour of complex disordered materials, such as porous rock, snow, or foam.
Highlights
As an original example, it has been shown how birds such as swallows build strong nests using their saliva to form cohesive bonds between mud granules, in an analogy with the mechanical properties observed in artificial cohesive granular materials.[4]Linking the mechanical properties of a disordered solid to its local structure presents difficulties
See DOI: 10.1039/ d1sm00458a ‡ These authors contributed to this study. It has been shown how birds such as swallows build strong nests using their saliva to form cohesive bonds between mud granules, in an analogy with the mechanical properties observed in artificial cohesive granular materials.[4]
We report here direct measurements of the constitutive relationship of the bonds between individual particles in this type of cohesive granular material, and demonstrate how to use these measurements to accurately predict the elastic properties of such a material
Summary
It has been shown how birds such as swallows build strong nests using their saliva to form cohesive bonds between mud granules, in an analogy with the mechanical properties observed in artificial cohesive granular materials.[4]. Linking the mechanical properties of a disordered solid to its local structure presents difficulties. The failure of a disordered material can suddenly change from ductile to brittle, depending on the density, strength, and plasticity of its contacts.[12,13,14,15] Experimentally, it is hard to study such effects in realistic systems: these are complex by nature and have intrinsic characteristics that cannot be systematically varied. Most progress in this field has been made in numerical modelling,[5,6,7,8,9,21] with the inherent difficulty that a too simplistic model might not capture the complexity observed experimentally, while an over-detailed one may not give any useful general law
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