The objective of this subject was to characterize, understand, model and simulate the exchanges at the interfaces, in relation to the multiphysics processes in each of the phases. First, thermo-diffusive couplings in non-equilibrium materials were treated, then chemical processes were taken into account, in order to deal with the relationships between diffusion, combustion and mechanical damage. Several aspects of the interaction between gas sorption and the behavior of polymers have been studied through theses in collaboration with the Hydrogenius laboratory at the University of Kyushu (KU) in Japan. A first study aimed to better understand how the mechanical load could modify the diffusion properties of a polyethylene exposed to high pressure hydrogen. Thermal analysis Desorption experiments have shown that even moderate mechanical loads influence the diffusion coefficient. A more advanced process of damage, i.e. the failure of decompression observed during the release of pressure in a rubber previously exposed to hydrogen at high pressure, was approached in a second study. A coupled diffuso-mechanical model, supported by unprecedented in situ experiments, was used to simulate the growth kinetics of the interacting cavities. A post-doc has developed finite element models based on microcomputer tomography (µCT) for the simulation of multi-physical thermo-diffuso-mechanical fields in composite materials with complex fibrous texture. The activity led to the development of voxel-based FE models at the sample level from high resolution µCT radiographic images. Concerning the combustion / damage coupling, the mechanical resistance of composite structures subjected simultaneously to mechanical load and to exposure to fire was modeled. In the field of fire safety, the interactions between the condensed and gaseous phases have been approached in collaboration with the University of Maryland, concerning the (auto) ignition of solid fuels and more recently the development of a digital combustion model. for a better capture of the successive transient stages of a fire. The visit of a visiting professor from the University of Moscow addressed the metal exposed to pure oxygen at high pressure, in order to understand the conditions of ignition and propagation of combustion. The process involves an induction period, followed by a static combustion phase, in a relatively thin layer of liquid metal and oxide and finally by dynamic combustion, when the liquid phase flows from the initial reaction zone.