The effects of dilatancy in composite assemblies as micropolar continua

Dilatancy is of importance for understanding the micromechanical behavior of materials such as cemented sand, mortar joints, and the interfaces of masonry-like structures. Rough interface contacts are able to result in dilatancy and lead to an increase in the material's volume. However, as far as the authors’ knowledge very few works are present regarding such phenomenon in composite materials. The present work aims at investigating the effect of dilatancy on composite materials with rigid particles connected by rough elastic interfaces. Different hexagonal shapes as rigid particles are considered by a series of geometric parameters. The stiffness properties of the rough interface can be obtained by employing a statistical distribution function of the roughness termed contact density model. A homogenization procedure based on an energetic equivalence criterion is used to derive the constitutive parameters. The homogenized continuum results to be a micropolar continuum with an additional degree of freedom (the microrotation) and is known to be able to give an effective result in modeling the behavior of materials with micro-structures. A 2D plane slope composed of material with various roughness interfaces is analyzed under the effect of dilatancy. This study shows the validity of the micropolar theory when considering the rough microstructure, which is essential for capturing more realistic behavior of composite materials.