Thermal debonding in compacted graphite iron: effect of interaction of graphite inclusions

This paper focuses on investigation of the interaction effect of graphite inclusions on failure of compacted graphite iron (CGI) subjected to thermal load. Although CGI has been used extensively in industrial applications and studied for many years, its failure under pure thermal load has not yet been fully understood, nor has the influence of interacting graphite particles on it. To analyse this phenomenon, a finite-element two-dimensional unit cell is constructed, consisting of two graphite particles presented as ellipses embedded in a metallic matrix. Each inclusion is surrounded by a thin layer that accounts for its interface in order to study its decohesion from the surrounding matrix. An elastoplastic behaviour is assumed for both graphite and matrix material, described by classical J2 flow theory of plasticity, whereas a traction-separation law is applied to the interface. The model is analysed numerically, with an emphasis on the influence of different parameters such as the inclusion size, the distance between the particles, and the combination of their shapes on thermal debonding, identifying critical combinations that either deteriorate or relieve the effect. The obtained results can provide significant knowledge on the response of CGI under thermal load at the microscale, contributing also to understanding of its macroscopic behaviour at elevated temperatures.