Hydro-mechanical network modelling of particulate composites

Abstract

Differential shrinkage in particulate quasi-brittle materials causes microcracking which reduces durability in these materials by increasing their mass transport properties. A hydro-mechanical three-dimensional periodic network approach was used to investigate the influence of particle and specimen size on the specimen permeability. The particulate quasi-brittle materials studied here consist of stiff elastic particles, and a softer matrix and interfacial transition zones between matrix and particles exhibiting nonlinear material responses. An incrementally applied uniform eigenstrain, along with a damage-plasticity constitutive model, are used to describe the shrinkage and cracking processes of the matrix and interfacial transition zones. The results showed that increasing particle diameter at constant volume fraction increases the crack widths and, therefore, permeability, which confirms previously obtained 2D modelling results. Furthermore, it was demonstrated that specimen thickness has, in comparison to the influence of particle size, a small influence on permeability increase due to microcracking. 1 arXiv:1707.09288v2 [cond-mat.mtrl-sci] 12 Oct 2017 imen thickness and particle size on the increase of permeability due to particle restrained shrinkage induced microcracking. For this purpose, a new coupled hydro-mechanical periodic network approach consisting of coupled structural and transport networks was developed. Periodic cells are known in the area of homogenisation [19,11], where it has been shown that periodic boundaries result in faster convergence of properties with increasing cell size than boundaries subjected to displacement or traction conditions. One of the new features of the present periodic approach is that not only the periodic displacement/pressure-gradient conditions were applied, but also the three-dimensional network structure has been chosen to be periodic for both the structural and the transport networks. Peviously, combinations of periodic network structure and periodic displacement conditions were developed only for two-dimensional structural networks [7]. The new three-dimensional coupled periodic approach allows for describing fracture patterns and resulting increases in conductivity independent of boundaries. For the transport network, the constitutive models were based on Darcy's law combined with a cubic law to model the influence of cracking on permeability [5]. MethodThe present numerical method for investigating the influence of particle restrained shrinkage induced microcracking on transport properties was based on three-dimensional periodic hydro-mechanical networks of structural and transport elements. For the constitutive model of structural elements, a damage-plasticity model was used [6]. The transport constitutive model used was Darcy's law combined with a cubic law [24] to model the increase of permeability due to fracture. The new feature of the present method is the extension of the coupled network approach proposed in [5] to a periodic cell of the shape of a recta...

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