Decoupling of water and oxygen diffusion phenomena in order to prove the occurrence of thermo-oxidation during hygrothermal aging of thermosetting resins for RTM composite applications

A novel experimental/numerical method is set up in order to decouple water and oxygen diffusion phenomena and to prove the occurrence of thermo-oxidation during hygrothermal aging of thermosetting resins for RTM composite applications. The method consists of creating artificial environmental conditions under pure water, pure oxygen and a water/oxygen mixture and in following the mass uptake of polymer samples during aging. Global and local (ultra-microindentation) mechanical properties of samples are then measured during and after aging, for each environmental conditioning. By analyzing the gravimetric curves with the aid of diffusion–reaction models and the results of mechanical tests, it is shown that water and oxygen diffusion phenomena are coupled in a complex way and that diffusion/reaction phenomena between water and oxygen take place during hygrothermal aging.