Ecological evaluation of the material concepts and production procedures as well as end-of-life and new-life scenarios for (bio) hybrid materials

© Fraunhofer WKI | Marek Kruszewski
Grist made of a hybrid duromer fiber composite plastic with carbon and natural fiber reinforcement.
© Fraunhofer WKI | Marek Kruszewski
Experimental set-up in the oven for pyrolysis - here of thermoplastic FRP of different geometries.

The objective of this project is the development of suitable respective recycling and disposal concepts for the materials and material combinations produced within the scope of the Fraunhofer Project Center in Wolfsburg, whilst simultaneously already taking the recycling aspect into account during the selection of the materials and the manufacturing processes.

For the innovative materials and combinations developed at the Project Center Wolfsburg, neither recycling scenarios nor an ecological evaluation have so far existed. In order to ensure the sustainable application of these materials, the economic and ecological assessment of their entire lifecycle, in particular with regard to possible utilization scenarios, is urgently necessary.

In addition to the development of appropriate end-of-life and new-life concepts for the manufactured components as well as for the material residues accrued during the process, the ecological and economic evaluation of the starting materials, material combinations and production processes is being undertaken.

In order to achieve these goals, we initially identify the most important materials and material combinations being utilized. For this, we develop end-of-life and new-life scenarios, taking into account during the preliminary stages the steps which are hereby necessary, such as dismantling. The possible recycling procedures include mechanical, chemical and thermal processes. The combination of different methods, for example mechanical recycling with pyrolysis, is also possible.

Following completion of these process steps, we also investigate the application possibilities and areas of utilization for recycled fibers, composites and residual materials. The recycling procedures can hereby be further optimized in order to increase the range of application possibilities for the recyclates and, for example, to optimize particular aspects, such as the energetic and economic outlay for the processes.

Finally, we consider the lifecycle of the materials - from the raw starting material through the process itself and on to recycling. The results achieved during the duration of the project flow directly into the respective ongoing parallel projects at the Project Center, with the effect that the recycling aspect can be incorporated as early as during the selection of the materials and processes.

Main focuses of the project:

  • Development of recycling concepts for lightweight structures
  • Pyrolysis
  • Mechanical recycling
  • Identification of suitable applications for recyclates
  • Ecological evaluation of the materials

Project results:

  • The knowledge gained from both processing methods allows conclusions to be drawn about the use of different epoxy resin duromers as well as the behavior of the reinforcing components under mechanical and thermal influence
  • In order to maintain the value of the carbon fibers or to reduce their depreciation compared to the new fibers, especially the long carbon fibers, pure mechanical recycling can be excluded, the pyrolytic process is to be preferred
  • On the other hand, due to the lower quality of flax fiber fabric, energy-intensive pyrolysis can be ruled out for this and comparable raw materials, as mechanical comminution requires less energy and allows almost complete recycling
  • Hybrid fiber reinforced duromers are to be examined in detail according to their structure. In the specific application both methods of recycling, the mechanical and the thermochemical, can be used
  • Neither of the two processing methods examined in this project, which are widely used in industry, constitutes a complete recycling cycle in itself but they do provide insights from current research in some areas

The project was funded by the state of Lower Saxony (funding number VWZN2990).