Flexafold Research Demonstrator, 2019

The Flexafold research demonstrator is an example of how biological folding and actuator principles can be transferred to a technical application, in this case a façade shading system. Flexafold consists of glass-fiber reinforced plastic with an embedded air cushion in the hinge/folding zones and a graded material structure. The air cushions are enclosed in elastomer to relieve material stresses in the component and to prevent delamination in the actuation plane. Flexafold is laminated with a TPU film for use as a façade component resp. to ensure weather stability.

The embedding of the air cushions in the material structure is inspired by the insect wing, likewise the folding principle: In the insect wing, hard and soft areas – consisting of the same basic material, but different in terms of distribution – can be found. The same applies to Flexafold: In the compliant zones, the material is composed in such a way that the elastomer content is higher and the fiber-reinforced composite is therefore more flexible than in the stiff component zones. In the stiffer parts, on the other hand, the proportion of glass-fiber reinforced plastic is higher. Graded material transitions additionally reduce the stresses that arise in the material during actuation.

Project Team
ITFT Institute for Textile and Fiber Technologies
University of Stuttgart
Prof. Dr.-Ing. Götz T. Gresser

ITKE Institute for Building Structures and Structural Design
University of Stuttgart
Prof. Dr.-Ing. Jan Knippers

DITF German Institutes of Textile and Fiber Research, Denkendorf
Prof. Dr.-Ing. Markus Milwich

EvE Evolutionary Biology of Invertebrates
Institute of Evolution and Ecology
University of Tübingen
Prof. Dr. Oliver Betz

Scientific Development
Larissa Born, Anja Mader, Axel Körner, Gundula Schieber, Paavo Bergmann

Publications within the scope of this project
Mader A, Born L, Körner A, Schieber G, Masset P-A, Milwich M et al. Bio-inspired integrated pneumatic actuation for compliant fiber-reinforced plastics. Composite Structures 2020;233:111558. https://doi.org/10.1016/j.compstruct.2019.111558.

Funding
This research has been funded by the Baden-Württemberg Foundation as part of the project BIAG ‘Bio-inspired adaptive façade shading systems’.