Analysis of Hydrothermal Ageing on Mechanical Performances of Fibre Metal Laminates

Fibre Metal Laminates (FMLs) are very interesting materials due to their light weight coupled with their high stiffness, high fatigue resistance, and high damage tolerance. However, the presence of the polymeric matrix in the composite layers and of polymeric adhesive at the metal/composite interface can constitute an Achille's heel for this class of materials, especially when exposed to a hot environment or water. Therefore, in the present article, aluminium/carbon fibre FML specimens were produced, aged by considering different hydrothermal conditions, and then, subjected to mechanical testing. The End-Notched Flexure (ENF) test was considered for this activity. It was found that the first ageing stage, consisting of submersion in saltwater, was very detrimental to the specimens, while the second stage, composed of high and low temperature cycles, showed an increase in the maximum load, probably due to a post-curing effect of the resin during the higher temperatures of the ageing cycles and to the dissolution of salt crystals during the subsequently ageing stages in distilled water.

Automated summary

Fibre Metal Laminates (FMLs) are lightweight materials with high stiffness, fatigue resistance, and damage tolerance. However, the polymeric matrix and adhesive at the metal/composite interface can be weak points, especially in hot or water environments. In this study, aluminium/carbon fibre FML specimens were aged under different hydrothermal conditions and subjected to mechanical testing. The results showed that submersion in saltwater was detrimental to the specimens, while high and low temperature cycles increased the maximum load due to resin post-curing and dissolution of salt crystals in subsequent aging stages in distilled water.