Speaker
Description
The importance of different length scales in materials science is well-recognised and subject of intense interdisciplinary research efforts. In these developments, multiscale modelling approaches take a key role as these enable the prediction of the effective material response based on detailed microstructure representations.
Motivated by the influence of microcracks and grain boundaries on effective electrical properties, the focus of this contribution is on the systematic development of generalised computational multiscale formulations for electrical conductors. In line with classic energy-based approaches for bulk material, it is shown that effective electrical conductivity tensors can be condensed from the underlying microstructure. The usefulness of the proposed formulation is demonstrated by taking into account experimental data. Extension of the detailed multiscale description of electrical conductors, grain boundaries and the associated strong discontinuities in the microscale fields are taken into account. This enables the systematic analysis of the Andrews method - one of the key approaches in materials science to study grain boundary resistivity and its effect on the electrical properties of polycrystalline materials. A theoretical foundation to the Andrews method is provided and its applicability and tacit assumptions involved are discussed along with resolving its core limitations. With material interfaces occurring at different length scales, eventually focus is placed on electrically conductive adhesives as a typical example of macroscale interfaces. These are key elements of electronic packages used in, e.g., automotive, communication and computing applications, with their distinct properties being rooted in the underlying intrinsic multiscale nature. By establishing energetic scale-briding relations, these macrosale composite interphases are approximated as zero-thickness cohesive interfaces. This generalises classic phenomenological traction-separation laws by relating the apparent electro-mechanical interface response to the underlying microstructure and lower-scale processes.
