The fraction and percolation of soft interfaces in granular composites containing polyhedral and ovoidal fillers: A theoretical and numerical study

Interface fraction and percolation around the fillers are the two significant factors related to the properties of granular composites and their solution is susceptible to the features of components. Understanding the relationship among the polydispersity of particulate components, interface fraction and percolation of interfaces is essential to the design and optimization of materials in a variety of fields. In this work, a numerical study on the influence caused by the morphologies, sizes and heterogeneities of individual phases is conducted, in which the composites are simplified as four-phase structures including polyhedrons, ovoids, soft interfaces and homogeneous matrix. By coupling these models and statistical geometry, the volume fraction ϕ_int of interfaces around the polydisperse binary-shaped fillers is derived theoretically and its reliability is verified. Afterward, the continuum percolation of interfaces in the polyphase systems are further studied and the critical percolation threshold ϕ_core,c is obtained. Based on the values of ϕ_core,c, the sensitivity of interface percolation to the shape- and size-diversities of particulate fillers is comprehensively analyzed and formulized by an analytical model. Through this in-depth study, some findings about the impact of shape- and size-heterogeneities of particulate phases on the interface features, which have not been presented previously, are clarified.