Fibre-reinforced plastics (FRP) are a central element of modern lightweight construction. Components such as wind turbine rotor blades would not be possible without this class of materials.
Saving of resources and higher resilience through optimal fibre orientation
FKV are special mainly because of their high strength combined with low weight. In addition, the fibres can be used to adjust the mechanical properties of the composite depending on the direction. This is because the composite is particularly strong in the direction of the fibres. Through the targeted selection of the fibre orientation, the component can thus be optimally adapted to its intended use. This also makes it possible to save weight and thus resources.
One starting point of this project is therefore the more precise adaptation of the fibre direction to the loads of a rotor blade. For practical reasons, fibre bundles have so far been sewn together into scrims (Fig. 1). These scrims are inserted into the rotor blade shape over a large area. Adjusting the fibre direction to the stresses in the component is only relatively rough in this way.
The utilisation of the fibre properties would be much more effective if all fibre bundles (rovings) could be laid independently of each other. This is possible through a process in which the fibre bundles are individually sewn onto a thin carrier material (Fig. 2). This technique is called tailored fibre placement and was developed by the IPF Dresden in the 1990s. This process is already used in industry for the production of small to medium-sized components. Rotor blades, which usually have a length of 50 to 100 metres, have so far exceeded the practical limits of tailored fibre placement.
In this project, however, it was possible to simulate the mechanical loads of a rotor blade and calculate the optimal course of the reinforcing fibres. To illustrate the results, a 2.5 metre long rotor blade was manufactured as a demonstrator (Fig. 3).
New approaches to recycling rotor blades
One disadvantage of FRP is that it is difficult to recycle. This is because the mostly used thermosetting plastics cannot be easily separated from the enclosed fibres. Therefore, only shredding of the components has been established so far. The shredded fibre-plastic mixture can then be used in limited quantities as an aggregate in the construction industry. Another possibility is thermal recycling. Neither would win a prize at a sustainability competition, of course.
Therefore, a second central topic of this research project is the investigation of composite materials that can be produced and completely degraded in a particularly resource-efficient way. It is being investigated how FRPs can be produced that consist of water-soluble glass fibres and biocompostable plastics and how their degradability proceeds under different conditions.