Membranes indeed experience harsh conditions in fuel cell operation such as an aggressive chemical environment and important mechanical stress.  
This aggressive environment results mostly from the formation of hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)) and its subsequent decomposition into highly reactive oxygen species (hydrogen H\({}^{\bullet}\), hydroxyl HO\({}^{\bullet}\) and hydroperoxyl HOO\({}^{\bullet}\) radicals) [5; 6; 7]. The radicals can then attack the most vulnerable sites of the PFSA, leading to the scission of polymer chains (backbone and/or side chains) [5] and thus to the membrane thinning [8; 9]. On the other hand, the humidity cycling and the stack clamping pressure exerted on the membrane during fuel cell operation cause important variations in the membrane water content, thus generating a mechanical fatigue that weakens its structure and can lead to the formation and growth of cracks and pinholes [10; 11; 12]. These days, it is well accepted that the membrane decomposition results from the synergistic interaction between the mechanical fatigue and the chemical degradation [1; 2; 13; 14; 15].  
The Fenton reaction is a widely-used ex-situ accelerated stress test (AST) enabling the reproduction of an oxidizing environment close to that observed during fuel cell operation [16]. It consists of reacting hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)) with iron ions (Fe\({}^{2+}\)/Fe\({}^{3+}\)) to form hydroxyl HO\({}^{\bullet}\) and hydroperoxyl HOO\({}^{\bullet}\) radicals with an accelerated way to rapidly evaluate the durability of PFSA membranes against chemical degradations. However, more complete and elaborate ex situ protocols are required to also consider the mechanical stress exerted on the membrane in fuel cells.  
In recent years, mitigation strategies have been developed to enhance the durability and performances of PFSA membranes. For instance, DuPont de Nemours\({}^{\text{\tiny TM}}\) and W. L. Gore & Associate Inc. have manufactured mechanically reinforced membranes by introducing a thin microporous layer of polytetrafluoroethylene (PTFE): the Nafion\({}^{\text{\tiny TM}}\) XL and Gore-SELECT(r) membranes, respectively. This process enables the elaboration of thinner membranes with a better mechanical endurance while their proton conductivity remains comparable with their unreinforced analogue [17; 18]. Furthermore, it has been demonstrated that the introduction of radical scavengers based on cerium species efficiently reduced the PFSA decomposition as a result of the radical attacks [19; 20; 21]. However, despite the presence of mechanical reinforcement and/or radical scavengers, the lifetime of composite membranes is still limited for long-term fuel cell operation [22; 23]. In addition, it is worth noting that even though mechanical reinforcement and radical scavengers are the most frequently used mitigation strategies to increase the durability of PFSA membranes and thus the PEMFC lifetime, other solutions have been proposed in the literature, for instance, new PFSA ionomers with structural features as well as semi-interpenetrating polymer networks have been recently developed to enhance membrane properties [24; 25] while a few authors improved the efficiency of the catalyst layers by using a highly dense, well-ordered and cone-shaped Nafion\({}^{\text{\tiny TM}}\) array [26].  
Nevertheless, among innumerable studies focusing independently on chemical or mechanical degradations these past decades, only a few have considered the effect of combined stresses on PFSA membranes [1; 2; 13; 14; 15]. The present study therefore aims to study the impact of a conjoint chemical-mechanical stress on composite and non-reinforced PFSA membranes. For that purpose, a specific home-made device was elaborated in order to couple mechanical and chemical stress exposure in conditions believed to reproduce fuel cell operation.