Function
Composite materials are used to provide an efficient, strong and relatively light blade structure.
Who supplies them
3A Composites, Airtech, Diab, Gurit, Hexel, Owens Corning, PPG, SGL and Zoltek.
Key facts
One type of manufacturing process for a blade is to make two full-length aerodynamic-shaped shells using a resin infusion process, large moulds and consumable vacuum bags. These shells are either glued around a central load-bearing spar or structural elements are incorporated into the blade shells and a strong load-bearing connection between them is provided using shear webs Another solution is a single infusion process to form the whole blade in one step.
Some insert the blade root connection prior to infusion whilst some drill and fit this afterwards.
Compromises are made between optimum aerodynamic shape (generally low aerofoil thickness) and optimum structural shape (higher aerofoil thickness).
Key parameters that define blade shape along the blade are chord (length of aerofoil cross-section), thickness of aerofoil cross section, twist (angular rotation of aerofoil) aerofoil shape and position of aerodynamic centre. These parameters are optimised during blade design.
A stepwise testing strategy for new blade designs is normally employed, where in turn blade materials, structural samples, blade sections and complete blades are tested under fatigue and extreme loads in order to verify design and ensure sufficient strength, a process that takes many months.
Repeatable blade quality and manufacturing time are two critical considerations during blade manufacture.
What’s in it
- Glass fibre, in uni-directional or woven fabric mat and/or prepreg form
- Carbon fibre (generally in prepreg form)
- Resin (either epoxy or polyester)
- Adhesive
- Closed-cell foam or balsa bulk fill
- Consumables