Study of the Thermomechanical Properties of Bimaterials (Metal/Ceramic)

Abstract

Bimaterial metal/ceramic assemblies are widely used in applications exposed to severe thermal environments, notably in the aerospace, power electronics and nuclear sectors. Due to the sharp contrast between the mechanical and thermal properties of the two materials (modulus of elasticity, coefficient of thermal expansion), these structures develop complex thermomechanical stress fields, which can initiate or propagate cracks.The present study focuses on the variation in stress intensity factor (SIF) associated with a localized plane crack in the metal part of a metal/ceramic assembly, under one-dimensional thermal loading. The aim is to quantify the influence of the thermomechanical properties of the bimaterial, the position of the crack relative to the interface, and the temperature distribution on the evolution of the SIF. The methodology is based on finite element modeling, with simulations carried out for different thermal loading scenarios (linear gradient, thermal shock), using typical materials such as steel/alumina. The results show that proximity to the interface significantly influences the amplification or attenuation of the SIF, depending on the direction of the thermal gradient and the contrast in properties. When the crack is close to the interface, an asymmetrical redistribution of stresses is observed, which may favor a deviation of the crack towards the interface or the ceramic. Taking these effects into account is essential for predicting the service life of these composite structures.