Damage methods swelling

There is only an alternative way of determining crosslink density by a non empirical method, using the theory of equilibrium swelling of a network in a solvent (Flory and Rehner, 1943). This method, usual in the domain of rubbers, needs the knowledge of a polymer solvent interaction coefficient proportional to (8p — 8S)2, which is not very easy to determine accurately. Furthermore, damaging by swelling stresses and the need to work at elevated temperatures complicate the analysis seriously for the usual thermosets... 

Damage mechanics principles have been applied extensively for well stability problems, especially for hard, brittle and fractured shale rocks. Constitutive models using damage concept, coupled with hydro-chemical swelling models, have been developed based on experimental results, and applied for design of drilling fluid density, combined with FEM methods (Liu, 1995). 

One fascinating observation by this author is that this type of damage is detected most readily by microscopic techniques or macro detection techniques. It seems to me that the development of methods to measure swelling of the upper cuticle layers may some day reveal this damage in a more sensitive manner than the techniques used today because, for a crack to appear in the hair, considerable damage at the molecular level must have occurred, leaving room for detection to a more sensitive degree than by the methods used today. 

Historically, surface treatments to improve adhesion of coatings to plastics consisted of mechanical abrasion, solvent wiping, solvent swell that was followed by acid or caustic etching, flame treatment, or corona surface treatment. Each of these treatments has limitations, thus providing a strong driving force for the development of alternative surface preparation methods. Many of the common methods mentioned are accompanied by safety and environmental risks, increased risk of part damage, and expensive pollution and disposal problems. 

In the case of composite laminates, new problems linked to the anisotropy of diffusion paths, the eventual role of interfacial diffusion and the role of pre-existing or swelling-induced damage appeared in the mid-1970s. The interest was mainly focused on the effect of humidity on carbon fibre/amine crosslinked epoxy composites of aeronautical interest. For the pioneers of this research (Shen and Springer, 1976), the determination of diffusion kinetic laws appeared as the key objective. Various studies revealed that, in certain cases, diffusion in composites caimot be modelled by a simple Pick s law and that Langmuir s equation is more appropriate. Carter and Kibler (1978) proposed a method for the parameter identification. At the end of the 1970s, the kinetic analysis of water diffusion into composites became a worldwide research objective. Related experimental results can be summarized as follows. 

Parts molded from polycarbonate can be cleaned, disinfected, and sterilized by most methods known in practical operation. With some materials, caution is advisable if aldehydes or phenols are active ingredients. Under certain conditions, damage in the form of stress-cracks can occur under contact with cleaning, disinfectant, and sterilizing media. They result in a reduction in mechanical strength. Moreover, there also other effects not always visible, such as initial swelling or chemical degradation in the plastic that can also impair mechanical properties. 

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