Micromechanistic modelling of the polycrystalline response of graphite under temperature changes and irradiation

A micromechanistic model has been applied to understand the relation between the properties of individual graphite crystals and the properties of polycrystalline graphite. The proposed model accounts for irradiation-induced creep as well as microcracking in both intragranular (parallel to basal planes) and intergranular positions. The two types of cracks were found to have a combined effect on the predicted macroscopic dimensional change and coefficient of thermal expansion (CTE) in both stressed and unstressed graphite. Model predictions were assessed against experimental data. Although further improvement in the simulation of irradiation creep may be required, the model provides useful insights for the mechanisms underlying the effect of macroscopic load on the CTE changes of unirradiated and irradiated graphite.