MS#05.7 Innovation in materials for wind blades

B. ENNIS¹, T. GRIFFITH²
¹ Sandia National Laboratories|² University of Texas - Dallas

Structures, structural integrity, materials

Existing wind systems use low cost materials to produce the lowest initial capital cost, resulting from the cost-driven nature of the wind industry. Controlling the cost and mass of wind turbine blades is critical to the continued progress of the industry and alternative material systems exist or are in development that show promise to support the industry needs of low cost, high performance, and improved sustainability. However, adoption of these material systems can be slow for various reasons including the limitations of failure models to estimate lifetime costs. Some material systems show improved performance but with increased material costs, requiring certainty in valuing associated blade mass reductions and/or improved durability and reduced lifetime costs.

As wind turbine blades have continued to increase in length, and exponentially in mass, the loading characteristics and damage tolerance have shifted in meaningful ways that stress the current materials in specific regions. The gravitational loading cycle (one per revolution) is now a critical design criterion along the edgewise direction of the blade, stressing the fiber reinforced polymer in these sections and the adhesives along the leading and trailing edges. Adhesives have a lower fatigue resistance than fiber reinforced polymers and are also quite susceptible to manufacturing variation and defects, making these sections of critical importance for statistical modeling. Damage arresting material systems and toughened resin systems (such as urethanes) reduce the probability of crack propagation after initiation, improving the damage tolerance of the blade compared to standard materials. In-field repairs from leading edge erosion are a main contributor to operation and maintenance costs for wind blades, despite a variety of material systems developed to prevent this damage. Finally, carbon fiber material systems have proven benefits for reducing blade mass but have high relative costs and embodied emissions.

Not only does it require confidence in cost models and failure probabilities to make material selections based on lifetime costs, but the drive towards low cost, durable materials inherently challenge material sustainability goals at the end of life. Material approaches that can improve overall sustainability of wind blades include separable resin systems, debonding adhesives, and bio-derived materials or natural fiber systems but currently require cost parity with traditional systems.

This mini symposium will be focused on coordinating talks related to advanced material systems being studied and/or developed for wind blade applications that show promise in reducing cost, improving durability, and/or increasing overall material sustainability.