Heat transfer and stress concentrations in a two-phase polycrystalline composite structure. Part I: Theoretical modelling of heat transfer

The aim of the paper is a numerical analysis of heat transfer in polycrystalline composites, containing metallic or elastic interfaces, i.e. metal-ceramic composites (MCCs) or ceramic matrix composites (CMCs). An example of MCCs is a two-phase material composed of brittle grains WC joined by the plastic binder Co. The work focuses also on the description of the heat concentrations in composites due to temperature changes, taking into account the real material internal structure, which includes grain shapes and interfaces. Under thermal loading the heat transfer in MMCs is mainly through metallic interfaces, where the heat flux concentrations occur due to different thermal properties of both phases. They can cause also stress concentrations and act as sources of damage initiators at the binder/carbide grains interfaces. The different contents of the interphase between elastic grains were taken into account in the analysis, starting from the interfaces of the small thickness: 2-4 m and volume content approximately 10% (e.g. Co), to the higher values up to 30%. The major conclusion is the following: the volume content of the metallic phase (Co binder) and its architecture (spatial distribution) inside the material strongly influences the heat transfer through the composites.