Radial pressure and thickness effects on the moisture diffusion in hollow composite cylinders

Abstract

According to the literature, the mechanical states (external or internal) have an effect on the penetration of moisture into a composite material through affecting both its main controlling parameters: the diffusion coefficient and the maximum moisture absorption capacity. In this article, a scale transition analysis is performed to investigate the coupled effect of the external/internal mechanical states, experienced by epoxy resin composite structures, on the moisture penetration process. The scale transition approach provides relations linking the plies strains to those of their constituents and homogenization procedures enabling to estimate the evolution of the plies diffusion parameters, from those of the epoxy, at any step of the moisture diffusion process. This work underlines the effects induced by the thickness of the considered composite structure. The respective contributions of the internal and external loads (in the case of a radial pressure, only) on the transient and permanent stages of the diffusion process are also investigated.

Coupling moisture diffusion and internal mechanical states in polymers – A thermodynamical approach

“…The moisture sorption results from coupled hygro-mechanical phenomena. The model developed here is the first enriched one, following many previous studies based on empirical approaches such as a the free-volume theory (Neumann and Marom, 1986;Youssef et al, 2009;Youssef et al, 2011).In contrast with previous work based on the thermodynamical approach, such as (Derrien and Gilormini, 2009), the present model accounts for the dependence of the polymer density on the mechanical states, which was previously neglected. The simulations reproduce the expected evolutions, as a function of the applied external pressure, of the maximum moisture…”

“…Therefore, considerable research efforts have been made in order to develop analytical models to predict the multi-scale mechanical states occurring during both the transient stage and the permanent regime of the moisture diffusion process in organic matrix composites subjected to hygro-mechanical loads (Jacquemin and Vautrin, 2002;Fréour et al, 2005). In this field of research, the most recent investigations (Aboudi and Williams, 2000;Derrien and Gilormini, 2009;Youssef et al, 2009Youssef et al, , 2011 focus upon taking into account, in the theoretical approaches, various features of hygro-mechanical coupling, observed during experimental studies, and in particular the dependence of both the moisture diffusion coefficient and the maximum moisture absorption capacity on the mechanical states (strains and stresses) (Marom and Broutman, 1981;Marom, 1986, 1987). These models aim eventually to enable the prediction of the long-term durability of composite structures subjected to hygroscopic loads.…”

The hygroscopic behavior of plant fibers: a review

“…In addition to that coupled diffusion model could be used in order to take into account the effects induced by mechanical states on the diffusion of moisture. Then, upcoming investigations could be focused on the use of more advanced multi-physics theoretical approaches dedicated to the modeling of the moisture uptake occurring while the heterogeneous, local swelling experienced by the reinforced polymer is accounted for Youssef et al ( 2009 , 2011 ); Sar et al ( 2012 , 2013 ).…”

Effect of mechanical states on water diffusion based on the free volume theory: Numerical study of polymers and laminates used in marine application

“…As in this study we do not consider any effect of the strain field on the maximal moisture absorption capacity of the polymer, it is obvious that at saturation, both models give the same results. Introducing an evolution of the mechanical parameters with respect to c(x, t) may enhance those disparities, as shown in [40,43,49]. In this first part, dicrepancies, at the local microscopic scale, between coupled and uncoupled models, were highlighted.…”