The market for wind turbine blades has grown at an average rate of 24% over the last 10 years. At the same time, turbines are increasing in size - production blades are now over 40 m long, with plans for even larger versions. The most important requirements for turbine blades are low cost, light weight, high fatigue resistance and adequate stiffness.

Many different types of composite materials have been employed for wind turbine blades, but laminated wood-epoxy construction meets this combination of properties very effectively. For the largest blades, an additional small amount of carbon fibre stiffening is necessary.

ACMC has been working with Vestas Blades for several years. The blade production process has been completely re-engineered, and is now based on resin infusion - a much quicker and cleaner alternative to hand lamination.

As a result of systematic large-scale experiments in the laboratory and factory, Vestas have gained enough confidence in resin infusion for the process to be used in full-scale production at their factory on the Isle of Wight. The total production cycle time for a 40 m blade has been reduced to only 24 hours. Work continues to further enhance process and quality control.

Further information:

• T Searle, J Spooner, S Grove, R Cullen and S Davy,
  Manufacture of large composite structures by vacuum resin infusion,
  24th International SAMPE Europe Conference, Paris, 01-03 April 2003, pp 113-121.
• Vestas sponsored EPSRC Industrial CASE studentship.
• Richard Cullen doctoral thesis:
  Air permeability of balsa core, and its influence on defect formation in resin infused sandwich laminates.