Mael Arhant

Marine Ageing Behaviour of New Environmentally Friendly Composites

In recent years several new materials have been proposed for marine applications. These include liquid infusible acrylics, basalt fibre and plant fibre-reinforced composites, and thermoplastic polyamide composites. In order to assess the long-term durability of such materials accelerated tests are used but the validity of this approach, widely accepted for traditional marine composites, must be checked. This presentation will describe results from ageing tests on these four materials, specifically developed for particular applications: acrylic composites and basalt and flax fibre composites for surface structures, and carbon-reinforced polyamides for deep sea pressure vessels.

Fatigue Behaviour of Acrylic Matrix Composites: Influence of Seawater

The recent introduction of liquid acrylic thermoplastic matrix resins which can impregnate fibre reinforcements using traditional infusion moulding offers significant potential for future composite structures in marine applications, such as marine energy devices. However, to date very few results are available to evaluate the long term durability of these composites in a marine environment. This paper describes results from a series of cyclic loading tests on glass and carbon fibre reinforced acrylic composites under both tension and four point flexural loading. Tests were performed before and after aging in natural seawater. The results were compared to results for a glass/epoxy used today in marine structures, and show a lower loss of both static and cyclic properties for glass/acrylic composites after seawater saturation. A carbon fibre reinforced acrylic composite was also tested. This showed excellent properties in tension, but poor out-of-plane properties due to manufacturing defects.

Prediction of mechanical property loss in polyamide during immersion in sea water

It is well known that the water absorption in polyamide leads to a large reduction in the mechanical properties of the polymer, which is induced by the plasticization of the amorphous phase. However, predicting such a loss in a marine environment is not straightforward, especially when thick samples are considered. This study presents a modeling study of the water absorption in polyamide 6 based on the free volume theory. Using this modeling coupled with a description of the stress yield changes with Tg, it is possible to predict the long term behavior of thick samples when immersed in sea water. Reliability of the prediction is checked by a comparison with experimental results.