RenWind - A new material systems for high output and low energy production process of wind turbine blades

The wind energy marked is a very fast growing marked with a yearly increase close to 20 %. One of the bottle necks is related to the production capacity of turbine blades. Producers of wind blades look for cycle time reduction to increase output and redu ce fixed costs. Epoxy resins are the dominant resins system used today for wind mill blade production. Compared to a vinyl ester system, epoxy gives viscosity increase during infusion, is a slow curing resin, requiring heated tools and post bake operati ons leading to long cycle times in the tools. Initial tests have shown that vinyl ester resins can reduce the cycle time with 30 % compared to epoxy resins. A switch to a styrene free vinyl ester resin system in blade production will in addition to shorte r cycle times and higher output range, also lead to substantial energy savings in the production process. What has prevented an increase in the use of vinyl esters in this market segment is the fact that laminates made of reinforced vinyl ester resins s uffer poorer fatigue performance than laminates made from reinforced epoxy resins. The fatigue resistance of infused blade laminates shows a strong sensitivity to resin, fabric and fiber content interactions. To realize the needed fatigue performance an d long term properties of vinylester resin composites for production of windmill blades, the interaction and adhesion to reinforcement materials will have to be improved. Thus, in order to be successful, two major innovations are needed: 1. One innovatio n is linked to the replacement of styrene as monomers. By using more environmental friendly monomers, epoxy resin systems can be replaced without the need of investing in extra ventilation systems. 2. The other novelty is the development of compatibilisi ng systems providing better adhesion and interface properties between the reinforcement fibres and the vinyl ester matrix to ensure enhanced fatigue and long term mechanical performance of the composites.