EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

SiC/SiC CMCs are currently under investigation for application in the aerospace and nuclear industries: for example, SiC/SiC started replacing some of the Nickel-based superalloy components used in the hot section of aeroengines. Internal interphases in SiC/SiC are designed to achieve the graceful failure required in structural applications. Consequently, understanding interfacial crack propagation and measuring interfacial properties such as the fracture toughness, friction or residual stresses is crucial to understand, predict and model the failure of these materials and their degradation in different environments. In SiC/SiC materials the fibres are normally coated with graphite-like C or hexagonal BN interphases to achieve the desired interfacial properties. In this presentation we show different micromechanical tests that can be used to propagate a stable crack at the interfacial region and measure the interfacial fracture toughness. This includes micro Double Cantilever Beam (DCB) and push out tests using an SEM in-situ setup. With these tests we measure the Mode I and Mode II interfacial fracture toughness and we can distinguish the different debonding and fracture events as they occur. With this work we highlight possible routes of optimisation of the new generation of CMC interphases based on their interfacial fracture properties.