Polymer lifetime prediction composites

Since the end of the 90 s, our group has been developing a non-empirical kinetic model, named KINOXAM, for the lifetime prediction of polymers and polymer matrix composites in their use conditions. The model is totally open. It is composed of a core, common to all types of polymers, derived from the now well-known closed-loop mechanistic scheme (/). Around this core, various optional layers can be added according to the complexity of oxidation mechanisms and the relationships between the structural changes taking place at the molecular scale and the resulting ones at larger scales (the macromolecular and macroscopic scales). 

Sichina [71] has discussed the applications of the dynamic mechanical analysis (DMA) to the prediction of polymer lifetimes and long-term performances, e.g., creep in gaskets, stress relaxation in snap-fit parts, modulus decay in composite structural beams, creep in bolted plates and heat deformation frequencies in structural parts. The ability of this system to generate master curves makes the prediction of product... 

Guedes R M. Creep and fatigue lifetime prediction of polymer matrix composites based on simple cumulative damage laws. Composites Part A Applied Science and Manufacturing, 39(11), 2008, pp. 1716-1725. 

The second study (Meghala and Ranganathaiah 2012) was dedicated to the evaluation of interfaces in poly(styrene-co-acrylonitrile) (SAN)-based ternary polymer blends using also positron lifetime spectroscopy. The method successfully applied for binary blends (single interface), mentioned above, was theoretically modified for ternary blends and experimentally verified by measuring free volume content in blends and their constituents. They tested the efficacy of this method in two ternary blends S AN/PVC/PMMA and SAN/EVA/PVC at different compositions. The effective hydrodynamic parameter evaluated using individual values turned out to be handy in predicting the overall miscibility level of a ternary blend. 

There have been many other empirical approaches to predict service life from accelerated test results, some based on relations between change in polymer properties and exposure variables (78). A simple empirical method of estimating lifetimes by comparison with control materials has recently been proposed (79). The method consists of exposing the test materials in the laboratory accelerated test device simultaneously with several control materials with similar composition and construction to the test material and having a range of failure times outdoors. It requires, as do all service life methods, that the accelerated test produce the same failure modes as natural exposure. In addition, rank correlation between the two exposures should be very high. If these conditions prevail and the service life of the control materials is well defined, the service life of the test material can be bracketed by two control materials. 

Owing to their cross-linked network, thermosetting resigns are principally known to be less susceptible to corrosion than some thermoplastic materials. Nonetheless, as shown by Bornbaum (2010), a prediction of long-term stability of polymers in fuel cell operation is hardly possible. Thus, the immersion or accelerated lifetime test should be applied on every novel material which has not been operated successfully in a fuel cell over a several thousand hours. These tests may save considerable amounts of time and can be performed before a fuel cell is set up. Nevertheless and finally, only a long-term test in fuel cells at various parameters and different conditions can provide ultimate certainty as to whether a newly developed composite is suitable or not. 

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