A discrete element thermo-mechanical modelling of diffuse damage induced by thermal expansion mismatch of two-phase materials

At the macroscopic scale, brittle media such as rocks, concretes or ceramics can be seen as homogeneous continua. However, at the microscopic scale, these materials involve sophisticated microstructures that mix several phases. Generally, these microstructures are composed of a large amount of inclusions embedded in a brittle matrix that ensures the cohesion of the material. These materials generally exhibit complex mechanical behaviors resulting from the interactions between the different phases of the microstructure. As a result, the macroscopic behavior of these media may be predicted considering an accurate knowledge of their microstructures. This paper proposes a model to study the impact of diffuse damage resulting from thermal expansion mismatch between the mixed phases. This type of damage (which is not catastrophic for the integrity of two-phase materials) may appear when heterogeneous materials are subjected to thermal cycles. This phenomenon involves a high amount of discontinuities and can not be tackled easily with the Finite Element Method (FEM). The Discrete Element Method (DEM) naturally accounts for discontinuities and is therefore a good alternative to the continuum approaches. However, the difficulty with DEM is to perform quantitative simulations because the mechanical quantities are not described in terms of the classical continuum theory. This study describes the approach used here to tackle this fundamental difficulty. The results given by the proposed approach are finally compared to experimental observations. (C) 2017 Elsevier B.V. All rights reserved.