Fraunhofer Institute for Wood Research
Wilhelm-Klauditz-Institut WKI
Fraunhofer Institute for Wood Research
Wilhelm-Klauditz-Institut WKI

Application Center for Wood Fiber Research HOFZET®

Technical Equipment

Robot-controlled fiber spraying facility

The fiber spraying facility is utilized in the production of “tailored composites”. We hereby specifically modify grammage, fiber type, fiber cutting length and fiber orientation to suit the component geometry. With the aid of the fiber spraying facility, we are able to develop and realize innovative (bio/hybrid) fiber composites and to integrate the technology into corresponding process chains. In addition to conventional high-performance fibers such as carbon, glass and aramid, cellulose-based fibers such as viscose, flax, hemp, etc. can also be cut and sprayed on using the fiber-spraying facility. As matrices, thermosetting resin systems or hybrid yarns, which are already combined with a thermoplastic, are applied.

Through targeted research, the procedure is applied to enable the quick and easy combination of materials. Few upstream process stages are hereby necessary, as the starting materials are simple rovings or yarns and the respective plastic components. We are therefore able to develop new customized material properties and to adapt these individually to the component. With this procedure, we realize a targeted load path-oriented component production. Expensive high-performance fibers should only be processed in the section of the component in which high strength or rigidity is necessary. The remaining zones are covered by other types of fibers (e.g. natural fibers), which have further advantages such as a lower price, good vibration behavior and a superior life cycle assessment.

In addition to the production of components, we are also carrying out research into the reinforcement and stiffening of existing structures. It is therefore possible, for example, for 2D organic sheets to be sprayed with this procedure prior to forming; this leads to increased strength and functionalization. In the case of organic sheet forming, limited draping properties are often the cause of component defects; with the aid of the fiber spraying facility, we can selectively remediate such problems. In addition, existing metal components can be sprayed and reinforced in this way. The wall thicknesses of the metal sheets are thereby reduced, and a higher lightweight construction potential is created.

The fiber spraying facility is located in the Fraunhofer Project Centre Wolfsburg, which is located at the “Open Hybrid LabFactory” (OHLF). Here, the entire process chain for lightweight structures in automobiles is developed and tested for large-scale production. The fiber spraying facility is part of the “textile production chain”.

 

Technical data

  • Reproducible, industrial cutting of natural fibers, carbon fibers, hybrid fibers, brittle fibers (glass, basalt), tough elastic fibers (viscose, thermoplastic fibers), etc.
  • Transport of four rovings simultaneously via separate hoses
  • Cutting capacity, depending on the type of fiber: 5 to 25 kg/h
  • Process-reliable fiber length: 1-100 mm
  • Infinitely-variable cutting length "on the fly" during the running process
  • Application of commercial and "newly-developed" polymer matrices (epoxy resin, unsaturated polyester resins, etc.)
  • Processing of 2C resin systems
  • Viscosity: < 3000 mPas