Elastic properties of particle-reinforced composites containing nonspherical particles of high packing density and interphase: DEM-FEM simulation and micromechanical theory

The physical and morphological properties of particles and interfaces can seriously impact the whole mechanical behavior of particle-reinforced composites. In this work, we devise a robust coupling model of the discrete element method (DEM) and the finite element method (FEM) to numerically investigate the effective elastic moduli of particle-reinforced composites consisting of elliptical particles of high packing density, compliant interfaces and homogeneous matrix. In the numerical model, a novel parametric equation for the topological geometry of an interface that is treated as an interphase model is formulated to realize a compliant (penetrable) layer with a constant finite thickness coated surrounding each elliptical particle. Additionally, a convenient strategy is implemented to cope with periodic boundary conditions containing numerous particles. On the other hand, we also propose a micromechanical theoretical framework to derive the effective elastic properties of such three-phase composites by incorporating the fraction of compliant interfaces that is theoretically computed by using the statistical geometry of composites. It is shown that our numerical and theoretical models lead to the prediction of elastic moduli of particle-reinforced composites with nonspherical particles of high packing density to a reasonable accuracy by comparing with available experimental data. Moreover, utilizing the proposed models, we systematically investigate the influence of the characteristics of particles and interphase such as the high packing density and geometries of elliptical particles, and interphase fraction, thickness and stiffness on the elastic moduli of particle-reinforced composites. We find that these physical characteristics play significant roles in determining the mechanical behavior of composites, suggesting that the properties of such materials can be tailored via proper composites engineering and design.