UD fabrics for 87.5-metre spar cap

Carbon fibre spar cap made with Saertex fabrics. © Saertex

Unidirectional fabrics specialist Saertex, based in Saerbeck, Germany, has supplied fabrics for the prototype production of a wind turbine blade with probably the longest carbon fibre spar cap made in vacuum infusion technology to date.

In April 2019, a wind turbine blade manufacturer in China successfully finished the production of an 87.5-metre spar cap. The spar cap is one of the key structures inside a rotor blade and takes up most of the mechanical load. The new record spar cap is made of carbon fibre to reduce the part’s weight and achieve higher stiffness which is essential for rotor blades of such extreme length.

The spar cap was designed by Berlin-based WINDnovation and represented a technical challenge because of its length, as well as its width of 800mm. The materials used for the production were a Saertex infusion-optimised carbon fibre UD 618gsm unidirectional non-crimp fabric, specially developed for the infusion of thick lay-ups and with increased z-permeability, along with a CTP AM 3325 A/B latent resin system with optimised viscosity and extended pot-life.

The spar cap was infused by VAP technology with Composyst’s VAP CS/E membrane which enables degassing of the resin during the entire infusion and eases resin distribution throughout the entire part as well as control of the resin content in the part, making the entire process safer.

The infusion process itself took less than two hours and was completed without any problems.