Abstract
There has been extensive use of polymer composite materials in the offshore and marine industries, but understanding their durability remains a significant challenge. The use of thermoplastic matrix composites is attracting growing interest due to their potential for being recycled. However, their long-term ageing behaviour in marine environments is unknown. As a first step, it is necessary to understand the effect of water absorption. In this work, we investigated two polymer composite materials, a glass fibre reinforced thermoset (Epikote epoxy resin) and a glass fibre reinforced thermoplastic (Elium). Flat panels were fabricated using the wet hand lay-up method, and coupons were extracted for the two composite materials. Elevated water temperatures were used to accelerate the ageing of the two composites, and their diffusivity was evaluated, as well as their glass transition temperature (Tg) at several intervals. To truly understand the behaviour of these materials, it is important to observe changes in the rate of moisture absorption over a range of temperatures and the contrast in Tg between the two different types of resin. The results show that exposure to various water temperatures produces changes in material properties (i.e., glass transition temperature) that are complex in nature. We measured an initial drop in Tg (16% for GF/Epikote and 9% for GF/Elium) followed by an increase, and we investigated the mechanics of that change. Another key finding was that the GF/Epikote composite showed a higher diffusivity than the GF/Elium composite. At 60°C, we found that the rate was nearly double: 21.9×10-13 m 2 s-1 for the GF/Epikote compared to 11.4×10-13 m 2 s-1 for the GF/Elium. The findings from this research will have direct implications for applications within the renewable energy sector, aiming to replace the current epoxy-based fibre composite used in wind turbine blades with a more durable and recyclable thermoplastic glass fibre-reinforced composite.