Jean-Claude Grandidier

Numerical Determination and Experimental Validation of a Technological Specimen Representative of High-Pressure Hydrogen Storage Vessels

A technological specimen representative of type IV high-pressure hydrogen storage vessels is developed. An analytical model is used to compute fiber orientations in the specimen in order to be as representative as possible of the stress level reached in a tank during pressurization. A three-dimensional finite-element model is used to determine the best stacking sequence with these fiber orientations. A validation is done by performing tests with digital image correlation in order to measure displacements on the lateral side of the specimen. A comparison between the calculated and experimentally found strain fields is made. The results obtained highlight the influence of stacking sequence on the development of damage and the difficulty arising in designing representative specimens.

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.