Composite materials

The work conducted within the framework of the «Composite Materials: acoustic emissions and life cycle projection" theme falls within the sustainability and life cycle projection of fibrous composite materials for carrying out long-term tests. It applies to composites with an inorganic or organic matrix. In order to achieve this goal, we not only need to quantify the damage and identify the different mechanisms that cause it, but we also need to define something that enables us to observe the damage in real time or simulate and model the evolution of this magnitude. Two further lines of research have been developed:

• Identifying the acoustic signature of the different damage mechanisms founded on an individual analysis of the EA signals, enabling us to define the appearance of critical mechanisms by identifying damage scenarios. This approach hinges on an acute description of the EA signals in the time, frequency and time-frequency domains and on the development of pattern recognition algorithms. This approach has recently been extended to crevice corrosion phenomena, leading to the development and submission of an RFCAM (Random Forest Classification for Acoustic Emission Monitoring) software programme.
   
• Life cycle projection in real time, founded on the analysis of the cooperative aspect of the acoustic emission, the observable of the damage state is acoustic energy. This approach hinges on accurately evaluating the energy produced by the source and analysing and simulating the acoustic energy. Work in the laboratory has highlighted the existence of a characteristic time or critical time at 50-60% of the life cycle of a CMC loaded with static and high-temperature fatigue, with the help of new indicators. Also, in order to characterise fibre breakage, a statistical approach to static and fatigue fracture founded on the analysis of fibre breakage in a wick subject to constant tensile stress has been put forward.