Stress-dependent electrical conduction in granular materials

Abstract

This dissertation is focused on electrical conduction behaviour in granular systems with the purpose of acquiring a fundamental understanding towards applications of granular materials. Performance in a range of engineering systems can be largely influenced by complex multi-physics interactions arising from microstructures of granular materials. The bulk of this dissertation is built on six published or submitted papers. After project background and related previous work introduced in Chapters 1 and 2, respectively, Chapters 3 and 4 deal primarily with the contact properties between rough surfaces. The obtained information at the interfacial scale serves as an experimental and numerical basis for modelling inter-particle contacts in granular media. Chapter 5 with the fifth paper presents the effects of network configuration on macroscopic network responses focussing on the dielectric universal scaling behaviour. In Chapter 6, the final paper shows a physical picture illustrating experimentally observed alternating-current universal scaling in conductive granular systems under different stress states. An effective numerical approach incorporating inter-particle interaction has been provided to simulate electrical responses of granular materials. The combination of the studies from macro-scale phenomena, network topologies, and inter-particle properties is presented leading to new physics-based constitutive models that contain lower scale information. This dissertation presents a new comprehensive understanding of conduction behaviour in granular materials by means of a physics-based framework combining features containing both experimental and numerical information obtained across various length scales, guiding design and optimisation of various granular materials