USA - New prepreg dedicated to the manufacture of wind turbine blades

Hexcel has developed a new prepreg specifically for the manufacture of wind turbine blades. HexPly® M19 is a major step forward in prepregs for wind energy as, according to Hexcel, it cures in 15-20 % less time than current prepregs used for the same application. The cycle time savings mean less energy is required to cure the prepreg and more blades can be produced in a week.

In addition HexPly M19 is diuron free, making it more pleasant to use, friendlier to the environment and compliant with new EU regulations that are being phased in over the next 11 years.

One of the major advantages of HexPly M19 is its low risk of uncontrolled exotherm. When curing composite laminates there is a risk of exotherm (excessive heat) being generated, particularly in thick laminates where the heat is slow to dissipate. The heat generated by the process further increases the reaction which can become a vicious circle and turn into an uncontrolled exotherm. To avoid this effect, cure cycles often involve a dwell (rest period) at low temperature (eg. 80 C) to allow the heat to dissipate and drive the reaction forward in a controlled manner, but this is time consuming and obviously prolongs the production process.

All of this can be improved by using HexPly M19, a low exotherm prepreg that is designed to reduce the overall cure cycle for the shell and spar by 15%. Hotspots are reduced during the cure process allowing more aggressive ramp up rates to be used to reach the higher temperature. The dwell with HexPly M19 is at a higher temperature and for a shorter time than with conventional prepregs. This allows for a controlled exotherm so that the higher temperature can be reached safely. The higher exotherm temperature enables the component to cure in less time. The final post-cure dwell time can also be reduced.

The shorter cure cycle means that savings in mould costs are achievable as less expensive tooling resins and tooling coatings can be used along with a cheaper tooling support system. All of this can result in 10% cost savings per mould. In addition the moulds are more durable with an increase in cycle life of up to 30%.

The improvement in cycle time for HexPly M19 has been proven in a full industrial environment, demonstrating that the required Tg could be achieved with a cure cycle that was one hour shorter than with the previous prepreg system.

HexPly M19 has the same excellent mechanical and handling properties as the established HexPly M9 prepreg range. It is suitable for the manufacture of shells, spars and the root end and is available with glass and carbon fibre reinforcement.

About Hexcel
Hexcel Corporation is a leading advanced composites company. It develops, manufactures and markets lightweight, high-performance structural materials, including carbon fibers, reinforcements, prepregs, honeycomb, matrix systems, adhesives and composite structures, used in commercial aerospace, space and defense and industrial applications.