The nanoscale stress field of interface cracks (InFraStress)

Interfaces between different materials are a fundamental building block for the performance and structural integrity of modern functional materials. These interfaces occur in a variety of forms ranging in size from single nanometers (e.g. in microelectronic devices) to the kilometer scale (e.g. in geological fault lines). However, the mechanistic understanding of interfaces and interface cracks is based on highly simplified elastic assumptions and phenomenological investigations. This applies in particular to interfaces between materials on the micro- and nanoscale. The aim of the project led by Dr. Michael Meindlhumer is to investigate the nanoscale stress and strain fields along interfacial cracks in a brittle-ductile composite material during the fracture process for the first time. On the one hand, the stress and strain fields that arise in a modern material system due to an interfacial crack under load are to be quantified for the first time, and on the other hand, these are then to be related to the elasto-plastic properties of the components of the bimaterial. Taken together, this should enable a deeper understanding of the crack propagation along interfaces. In order to achieve the project goal, a combination of different micromechanical testing techniques is used: in situ scanning electron microscopy will investigate the dynamic fracture process along interfaces, while the stress and strain fields will be quantified by means of in situ synchrotron X-ray nanodiffraction during deformation. In addition, the experimental data will be complemented by finite element model calculations. The combination of these techniques should lead to a deeper understanding of interfacial cracks and validate existing models for the first time using quantitative nanoscale resolved stress and strain data. The mechanical data generated in this way will subsequently help to create new design criteria for modern structural and functional materials.