Demonstrating re-use of thermoplastic composites originating from wind turbine blades

Abstract

The goal of this thesis project was to explore how material originating from thermoplastic composite wind turbine blades (TPC WTB) can be reshaped. The insights gained during exploratory activities were used to design a re-use application. The demonstrator model should inspire people to develop other applications and build upon the foundations laid here.
While wind turbines are a big contribution to the green energy supply, their blades form a problematic waste stream of hard to recycle material. One upcoming blade design innovation aimed at enhancing recycling, that of thermoplastic composites, has opened up a new opportunity in circular end of life strategies: structural re-use through reshaping.
A reference TPC blade was drafted based on insights gained from literature and experts, which defines characteristics like material composition, structure and curvature. These were needed for subsequent material tinkering activities aimed at understanding the material, exploring forming limits and process parameters (Figure 1).
 
These findings, together with material properties and opportunities and threats were combined in a SWOT matrix and design requirements. Blade segmentation was used to make a panel classification table which contains information on panel characteristics which were later used in designing an application. To be able to shape smaller radii, it was decided to split the top layers from the sandwich panel which resulted in much thinner laminates but also more unused material (15 wt%).
After a solid understanding of the material was built, an application could be designed. Standard ideation tools like brainstorming were used but also less standard methods aimed at finding applications yielded diverse application ideas. Following the design vision, one idea was selected: a lamppost. Embodiment of the lamppost based on earlier findings and a norm resulted in a conceptual application design. To prove the feasibility of this application, the strength and stiffness of the post were calculated to comply with the NEN EN 40 norm.
This design was translated to a demonstrator which can be seen in Figure 2. The goal of this demonstrator was to evaluate the performance of the material in reshaping and to simultaneously inspire people to develop new applications, which was validated using interviews. An evaluation of the amount of material used in this application showed that about a third of the yearly supply of WTB material saturates the yearly demand of lamppost.
It can be concluded that the material performs well in reshaping single curved geometries, however reshaping could be problematic for double curved surfaces. The smallest single curved radius tested was 30mm while the largest double curved radius which was tested was 1000mm. A meaningful application which makes use of the material’s value can be made within the reshaping limits while also utilizing a significant amount of blade waste.