Hygrothermal ageing of composite structures. Part 1: Technical review

The aim of this work is to review the literature of hygrothermal ageing in composite structures, focusing on the effects of moisture absorption on mechanical properties, damage behavior and degradation mechanisms responsible for changes in performance. Potential causes that can lead to failures are detected and the main variables that influence the ageing are taken into account: these include the surrounding environment and climate conditions, which appear to be determinant. Secondly, a case study analysis on previous accidents involving aircraft composite structures damaged by moisture is presented. This reveals that some components, such as sandwich panels and adhesive-bonded-joints, are particularly affected by hygrothermal ageing, and thus require a detailed assessment in terms of humidity deterioration. Further insights on the main industrial applications of these components, such as wind and tidal turbine, are showcased and crucial issues are highlighted. Moreover bio-composites behaviour in harsh environments are analyzed, showing drawbacks and advantages.