Hygrothermal Aging and Thermomechanical Characterization of Tidal Turbine Blade Composites

Strategic Insights -

A new research study has investigated the hygrothermal aging behavior and thermomechanical properties of glass fiber-reinforced epoxy and thermoplastic composite tidal turbine blades, which were previously deployed in a marine environment. The research, funded by the US Department of Energy Water Power Technology Office, has provided valuable insights into the effects of moisture on the long-term structural integrity of tidal turbine blade composites. The study's findings have significant implications for the design and development of marine renewable energy composites, emphasizing the critical influence of moisture on long-term structural integrity and the need for optimized material systems in harsh marine environments.

Key Takeaways:

  • The study found that thermoplastic composites exhibited lower overall water absorption (0.78% vs. 0.47%) but had significantly higher diffusion coefficients than epoxy (2.1 vs. 12.1 x 10^-13 m^2s^-1), suggesting faster saturation in operational environments.
  • Dynamic mechanical analysis (DMA) results demonstrated that water ingress caused plasticization in epoxy matrices, reducing the glass transition temperature and increasing damping, while thermoplastic composites showed more stable thermal behavior.
  • Tensile testing revealed substantial reductions in ultimate strength (40%) for both materials after prolonged water exposure, with minimal change in elastic modulus, highlighting the role of matrix degradation over fiber reinforcement.
  • XCT image analysis showed that both composites were manufactured with high quality, with no large voids or cracks present, and the degree of misalignment was low.
  • The study compared the performance of epoxy and recyclable thermoplastic tidal turbine blades in a marine environment, highlighting the importance of material and manufacturing choices on long-term marine durability.
  • The research concluded that these findings inform future marine renewable energy composite designs, emphasizing the critical influence of moisture on long-term structural integrity and the need for optimized material systems in harsh marine environments.

Statistics:

  • Hygrothermal aging experiments revealed that thermoplastic composites had a diffusion coefficient of 2.1 x 10^-13 m^2s^-1, while epoxy had a diffusion coefficient of 12.1 x 10^-13 m^2s^-1.
  • DMA results showed that the glass transition temperature of epoxy matrices was reduced from 112 °C to 104 °C after water exposure, while thermoplastic composites maintained a stable glass transition temperature of 87 °C.
  • Tensile testing revealed a 40% reduction in ultimate strength for both materials after prolonged water exposure.
  • XCT image analysis showed that both composites had a degree of misalignment of less than 10%.

Sources:

  • "Hygrothermal Aging and Thermomechanical Characterization of As-Manufactured Tidal Turbine Blade Composites." Journal of Marine Science and Engineering, vol. 13, no. 9, 2025, p. 1790.
  • National Renewable Energy Laboratory. (2025). Data on Marine Science and Engineering Reported by Researchers at National Renewable Energy Laboratory. Journal of Engineering, 416.