Experiments have indicated that the diffusion properties of a penetrant organic matrix composite system may change with time due to evolution of the internal mechanical strain states experienced by the constituting matrix of the composite plies. A multi-scale approach coupling the internal mechanical states, predicted by continuum medium mechanics, and their localization at the ply-constituent scale to the traditional Fick's law governing the moisture diffusion process was used in order to achieve the modeling of the response of composite laminates submitted to environmental hygroscopic loads, from the transient part of the diffusion process to its permanent stage. Various numerical practical cases were considered: the effects of the internal swelling strains on the time-and space-dependent diffusion coefficient, maximum moisture absorption capacity, moisture content, and states of internal stresses are extensively studied and discussed.

pos ite lam i nates, mois ture dif fu sion, hy gro scopic stresses, soft en ing, mod el ing The ef fects re lated to the evo lu tion of the mois ture-de pend ent hygroelastic prop er ties of com pos ite plies consti tut ing a fi ber-re in forced ep oxy lam i nate on the pre dicted stress states in the struc ture dur ing the tran sient stage of hy gro scopic load ing are in ves ti gated. The ap proach pro posed in volves the cou pling of the clas si cal con tin uum me chan ics for mal ism to the Eshelby-Kröner self-con sis tent scale tran si tion model. An in verse scale tran si tion model is used to de scribe the evo lu tion of lo cal hygroelastic prop er ties of the ep oxy ma trix as the pro cess of mois ture dif fu sion pro ceeds. The scale tran si tion re la tions al low one to de ter mine the lo cal distri bu tion of stresses in the con stit u ents (fi ber and ma trix) of each ply of the lam i nates con sid ered from the distri bu tion of mac ro scopic stresses. Nu mer i cal sim u la tions show that the ac count (or not) of soft en ing of the com pos ite struc ture un der hy gro scopic load ings sig nif i cantly af fects the multiscale stress states pre dicted.