Fiber-reinforced plastics are characterized primarily by high stiffness and strength as well as the manufacturing in integral construction. Thus high-performance components can be produced close to final contour in one process step. However, for deployable systems it is still necessary to connect single components with mechanical joints. Consequently, cost-intensive additional process steps are required and a material-independent weak point is generated by the joint. An example of application are adaptive shading systems for complex, doubly curved, exterior façades. The most common cause of failure of such articulating components is mechanical abrasion in the joints leading to failure of the entire component group.
Biology shows that deployable systems could work without mechanical joints by local adaptation of rigidity. Opening and closing movements of arthropod wings and carnivorous plants are based on folding along interconnecting bending zones with lower rigidity compared to the moving parts. This anisotropy is due to the internal structure of plants and arthropods, which resembles fiber-reinforced plastics with a shaping matrix enveloping reinforcement fibers. The intensive investigation of two biological models, the shield bug and the waterwheel plant, allows to identify biological construction principles which inspired the development of technical, deployable systems.
For technical implementation various combinations of fibers and matrices are investigated with regard to take advantage of the anisotropy of fiber-reinforced plastics. The decisive factors for the application as adaptive building envelope in addition to UV- and temperature-resistance are in particular mechanical properties. To demonstrate the essential bending properties, the deformation of fiber composites in folding mechanisms is imitated by a specially developed two-point bending test. The research results have been implemented in a new fiber-reinforced plastic. Defined flexible bending zones are implemented in a rigid three-layer composite of fibers and plastics. The Flectofold, a first demonstrator for adaptive façade shading systems, proves the functionality.