Taking these factors into account, we select one or more material stages of a fiber-matrix combination in order to improve the overall recycling potential of the end product.
During the course of the preceding project “inBETWEEN”, it became apparent that the utilization of discarded textiles is still difficult. This is because there are currently no large material flows of single-variety waste textiles suitable for the production of functional components made from fiber-reinforced plastic. The type of textile has a major influence on the processing procedure, the fiber-matrix adhesion, and the mechanical and sensory properties of the fiber-reinforced plastic. As a result, the textiles must exhibit certain material properties in a consistent, predictable quality - particularly for mass applications with specific requirements, such as vehicle construction or industrial furniture manufacturing. In addition, discarded textiles are often not available in sizes that are big enough to be used as reinforcing fabrics in large-area components, such as a car door or a wind-turbine rotor blade. In this project, we are therefore focusing on renewable natural fibers such as flax.
For the plastic matrix, the situation is somewhat different: Here, single-variety, large material flows of potentially suitable recyclates already exist, for example from polypropylene (PP). Consequently, this is where our focus lies.
In the next step, we define a number of recyclable material stages for each of the selected fiber-matrix combinations that are to be used for product development. Conceivable materials include films, organic sheets, compounds made from flax-fiber PP, and recyclates produced from these materials. The material stages are produced at the Fraunhofer WKI. Subsequently, an evaluation is carried out on the basis of two overriding aspects:
- Evaluation of design quality (project partner “Studio Jonathan Radetz”)
- Determination and evaluation of technical properties such as strength and flowability. This enables statements to be made not only with regard to their dimensioning (e.g. material thickness vs. stiffness), but also with regard to process limits, for example how well a mold can be filled with the melt by means of injection molding.
With the selected and best-evaluated material stages, we conceptualize seating furniture with defined functions:
- Necessary functions: possible to sit on
- Desired functions: haptic and aesthetic functions, taking into account the specific area of application
The knowledge gained in the project regarding the design and selected technical qualities of the various material stages allows us to specifically utilize material stages in order to fulfill the functions. As a result, one or more designs for the seating furniture are created.
The conclusion of the project is the practical implementation of a selected design as a functional demonstrator. To be precise: We produce an item of seating furniture, thereby verifying the success of the development method (proof of concept).
Fraunhofer Institute for Wood Research 
