Olga Guseva

Service life prediction for aircraft coatings

A model with three stress types, the temperature, UV and aerosol, for estimating the service life of organic coatings under service conditions has been proposed. The model has been applied to the estimation of the service life for aircraft coatings concerning loss of gloss. The results obtained from a unique natural exposure programme for a reference polyurethane coating have been compared with the results from the specially designed accelerated ageing tests, which were performed with a new designed and constructed weathering device. As a special point of interest, the influence of sulphuric aerosol, which has simulated the stratosphere conditions after a big volcano eruption, on the service life of the reference coating has been investigated.

The influence of platelet disorientation on the barrier properties of composites: a numerical study

Direct finite element calculations are carried out to study the relationship between the platelet orientational distribution and the overall effective barrier properties (gas permeability) of mineral filled composites. We consider multi-inclusion computer models with microstructures representative of the dilute, semi-dilute and concentration regimes. In the dilute regime, our numerical predictions validate the results of multiple scattering expansion theory. For the semi-dilute and concentration regimes representative of most real composites, we present numerical estimates quantifying the difference between the barrier properties of composites with fully aligned and randomly oriented platelets. Our numerical results can also be used to quantify the effect of the geometric factor on the gas barrier properties of polymer–mineral hybrid nanocomposites.

Analysis of the environmental parameters for aircraft coatings

Temperature, UV radiation and pollutants play a major role in the degradation of aircraft coatings. The UV radiation at flying altitude is more intense than at ground level. An analysis of the radiation spectrum was used to choose the appropriate lamp type for artificial weathering in the laboratory. For the pollutants we examined the fact that the service life of aircraft coatings was considerably reduced in the years following the eruption of the volcano Pinatubo. It is shown that sulphuric-acid-aerosol droplets dispersed in the stratosphere were the main cause for that damage.

Matching thermal expansion of mica–polymer nanocomposites and metals

Finite element numerical simulations have been carried out to demonstrate that by the dispersing of a small amount of exfoliated muscovite mica platelets in a solid polymer one can considerably reduce and even match the thermal expansion coefficients of metal and polymer components of hybrid polymer–metal structures. In practice, such mismatch reduction may lead to the extension of the service life of hybrid polymer–metal structures. Computer models comprised of a random dispersion of fully aligned round muscovite mica platelets have been studied. It was found that the decrease of the thermal expansion for such nanocomposites is controlled by the product of the aspect ratio and the volume fraction of the mineral platelets, and that the dependence can be accurately described by a stretched exponential master curve, thus considerably facilitating the task of designing mica–polymer nanocomposites with tailored thermal expansion.