03 - Damage diagnostic and lifetime prognosis for ceramic matrix composite with Acoustic Emission during long-term mechanical tests at intermediate temperature

摘要

Damage of composite materials is a key factor for the durability in service. It is therefore essential todefine the most suitable damage indicators and to develop models to estimate the Remaining UsefulLifetime from analysis of precursor events resulting from damage. Acoustic emission is relevant to thedevelopment of the Prognostic and Health Management because it allows knowing the state of damageof a composite structure in real time. This work is dedicated to lifetime prediction using AE for long-termtests on CMC during static and cyclic fatigue tests. New indicators of damage have been defined, basedmainly on acoustic energy analyses. These indicators highlight critical times (around 50 % of thecomposite lifetime) allowing an evaluation of the remaining lifetime. A linear correlation is observedbetween these critical times and the lifetime duration. For a prognostic phase, the results obtained withthis empirical law are compared to those obtained with a power law such as a Benioff law. Moreover,the clustering of acoustic emission, using a random forest approach, makes possible to identify themechanism responsible for this critical time. For the static fatigue test, the critical time around 50 %correspond to the delayed failure of fibres.