Computational homogenization of the debonding of particle reinforced composites: The role of interphases in interfaces

Abstract There are four primary factors which influence the macroscopic constitutive response of particle reinforced composites: component properties, component concentrations, interphases, and interfacial debonding. Interphases are often a byproduct of surface treatments applied to the particles to control agglomeration. Alternatively, in polymer based materials such as carbon-black reinforced rubber, an interphase or "bound rubber" phase often occurs at the particle-matrix interface. This interphasial region has been known to exist for many decades, but is often omitted in computational investigations of such composites. In this paper, we present an investigation into the influence of interphases on the large deformation response of particle reinforced composites. In addition, since particles tend to debond from the matrix at large deformations, we investigate the influence of interfacial debonding on the macroscopic constitutive response. The investigation considers two different microstructures; both a simplified single particle model, and a more complex polydisperse representative unit cell. Cohesive elements, which follow the Park-Paulino-Roesler traction-separation relation, are inserted between each particle and its corresponding interphase to account for debonding. To account for friction, we present a new, coupled cohesive-friction model and detail its formulation and implementation. For each microstructure, we discuss the influence of the interphase thickness and stiffness on the global constitutive response in both uniaxial tension and simple shear. To validate the computational framework, comparisons are made with experimental results available in the literature.