Aging of composites — Study mechanisms and methodology

Establishing criteria and models for predicting the long-term behavior of organic matrix composites (OMCs) with fibrous reinforcements is a major challenge for designers and users alike. Optimizing the performance of equipment, and consequently of the materials used to make it, over increasingly long periods of time requires increasingly reliable models that take into account all the stresses and degradations induced by their propagation in service. This behavior must be fully integrated into the certification of CMO structures prior to their use.

Durability involves complex phenomena, which means that we need to understand the degradation mechanisms involved and combine knowledge of chemistry, physical chemistry, mechanics and numerical simulation to produce reliable behavior prediction models, leading to the cooperation of multidisciplinary teams in their study. To better predict their long-term behavior, it is necessary to carry out accelerated aging and correlate it with the aging of these same materials, in their usual structural configuration and conditions of use. The chosen acceleration factor must not alter the material's evolutionary mechanisms, and all influencing factors must be explored and their mode of action understood. Feedback on their behavior in use is essential to validate the predictive models that can be developed.

This article attempts to define the mechanisms and phenomena likely to contribute to the degradation of composite material properties, as well as the aging method and means to be used to establish reliable predictive models of long-term behavior, or at least to predict behavior in use. It focuses in particular on CMOs used for structural applications, and uses a variety of examples to describe the aging phenomena likely to be encountered in service. The application of the long-term behavior prediction method and test methods to specific examples is reported in the article [AM 5 321] .

This article complements the various articles on ageing studies [AM 3 150] , ,