Modelling the mechanical properties of interface structured multi-layer composites under large deformations

• Applicant: Dr.-Ing. Jana Wilmers
• Subject Area: Mechanics ; Coating and Surface Technology
• Term: from 2020 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 449062206

Structuring and patterning of layers and interfaces in multi-layer systems can induce remarkable deformation properties in individually stiff and inflexible materials. This utilises an apparently simple – however difficult to achieve – principle: The structure is deformed not the stiff material.Interfaces exhibit properties that can significantly vary from those of the bulk material. Consider for example the role interfaces play in corrosion and wear resistance or their influence on electrical and thermal conduction in a material. By structuring these interfaces not only the interface to volume ratio can be tailored but also additional functionality can be induced, for instance the large deformation capabilities achieved in the structures considered in this project.Utilising such structures to their full capability can only be achieved with a comprehensive understanding of the involved mechanical principles that will allow tailored material development and optimisation. Tasks that need to be tackled in this context include maximisation of available functional material, i.e., optimisation of the spatial distributions of stress and displacement, as well as improving life time under a variety of loading cases.The goal of this project therefore is modelling and investigation of structure-property relationships in composite materials with structured interfaces. Based on numerical studies, the underlying mechanical (and later thermal and electrical) mechanisms can be elucidated, thus, forming the theoretical basis for development of structured multilayer composites capable of large deformations. Continuum mechanical modelling and finite element analysis will be employed to study deformation mechanisms and failure by cracking and delamination. Algorithms for automatised generation of representative volume elements will be developed which facilitate variation of numerous geometry and material properties. The influence of these geometrical and material parameters on the mechanical properties, the deformation capabilities, crack propagation and failure behaviour will be analysed. Thereby building a theoretical numerical framework for the development and optimisation of structured multi-layer composites. The project will focus on application of these structures in micro electronics but as the analysis is based on geometry-mechanics relationships, it is expected that gained insights are applicable to a variety of material classes and application fields.

• DFG Programme: Research Grants