The impacts of long-term submersion in seawater on thermoplastic-matrix composite materials

Tidal turbine blades operate under challenging conditions as integral components of tidal energy converters. Constant submersion in seawater and exposure to high loads necessitate thick wall sections (10–100 mm) throughout blades, particularly at the root. Thermoset matrices are conventionally used in vacuum infusion processing to form durable fibre-reinforced composite components with structural integrity. However, the cross-links that provide these desirable properties also prevent melting and reshaping, limiting recyclability compared to thermoplastics. Advancements in recyclable liquid thermoplastic resins (LTPR) offer the opportunity for more sustainable material solutions for composite blades. Understanding the effects of prolonged submersion in saltwater on LTPR composite materials is critical for their application in thick-section structures used in the marine and tidal energy industries. This paper investigates the water uptake of two glass fibre/LTPR composites, manufactured with different grades of the same acrylic-based resin, Elium® 188 XO and Elium® 191 XO/SA, using accelerated ageing testing to simulate 10 years of submersion. GF/Elium® 191 XO/SA reached saturation more rapidly than GF/Elium® 188 XO, resulting in a greater total mass increase of 1.00% compared to 0.54%, with standard deviations of 0.65% and 0.02%, respectively. This study is part of an ongoing, longer-term assessment aimed at experimentally simulating a 20-year lifespan, representing the full design life of tidal turbine blades.