The Institute for Computational Design (ICD) and the Institute of Building Structures and Structural Design (ITKE) of the University of Stuttgart have constructed a bionic research pavilion as part of a series of research pavilions which showcase the potential of novel design, simulation and fabrication processes in architecture.
The project was planned and constructed within one and a half years by students and researchers within a multi-disciplinary team of biologists, paleontologists, architects and engineers in collaboration with the University of Tübingen, the Karlsruhe Institute of Technology (KIT) and the Institute of Textile Technology and Process Engineering ITV Denkendorf.
The focus of the project is a parallel bottom-up design strategy for the biomimetic investigation of natural fiber composite shells and the development of novel robotic fabrication methods for fiber-reinforced polymer structures. The aim was the development of a winding technique for modular, double-layered fiber composite structures, which reduces the required formwork to a minimum, while maintaining a large degree of geometric freedom. Therefore, functional principles of natural lightweight structures were analyzed and abstracted. Through the development of a custom robotic fabrication method, these principles were transferred into a modular prototype pavilion.
This investigation of natural lightweight structures showed that the elytron, a protective shell for beetles’ wings and abdomen, proved to be a suitable role model for highly material-efficient construction. The performance of these lightweight structures relies on the geometric morphology of a double-layered system and the mechanical properties of the natural fiber composite. The shells of multiple beetle species were analyzed and compared; the underlying structural principles were identified and translated into design rules for structural morphologies.
Material and structural logic
Based on the differentiated trabeculae morphology and the individual fiber arrangements, a double-layered modular system was generated for implementation in an architectural prototype. Through the development of computational design and simulation tools, both the robotic fabrication characteristics and the abstracted biomimetic principles could be simultaneously integrated in the design process.
Glass and carbon fiber-reinforced polymers were chosen as building material, due to their high performance qualities (high strength to weight ratio) and the potential to generate differentiated material properties through fiber placement variation. Together with their unrestrained moldability, fiber-reinforced polymers are suitable to implement the complex geometries and material organizations of the abstracted natural construction principles. Conventional fabrication methods for fiber composite elements require a mold to define form. However, this method proves to be unsuitable to transfer natural construction principles into architectural applications, since they usually involve unique elements that would require extensive formwork and prohibitively complex molds.
Robotic winding process
For the fabrication of the geometrically unique, double-curved modules, a robotic, coreless winding method was developed, which uses two collaborating 6-axis industrial robots to wind fibers between two custom-made steel frame effectors held by the robots. While the effectors define the edges of each component, the final geometry emerges through the interaction of the subsequently laid fibers. The fibers are at first linearly tensioned between the two effector frames. The subsequently wound fibers lie on and tension each other which results in a reciprocal deformation. This fiber–fiber interaction generates doubly-curved surfaces from initially straight deposited fiber connections.
The order in which the resin impregnated fiber bundles (rovings) are wound onto the effectors is decisive for this process and is described through the winding syntax. The specific sequence of fiber winding allows the ability to control the layout of every individual fiber leading to a material-driven design process. These reciprocities between material, form, structure and fabrication are defined through the winding syntax, which therefore becomes an integral part of the computational design tool.
The effectors are adjustable to various component geometries, leading to only one reconfigurable tool setup for all 36 elements. Coreless filament winding not only saves substantial resources through the needlessness of individual molds, but in itself is a very material efficient fabrication process, since there are no waste or cut-off pieces.
The specific robotic fabrication process includes the winding of six individual layers of glass and carbon fibers. A first glass fiber layer defines the elements geometry and serves as formwork for the subsequent carbon fiber layers. These carbon fiber layers act as structural reinforcement and are individually varied through the fibers anisotropic arrangement. The individual layout of the carbon fibers is defined by the forces acting on each component which are derived from FE Analysis of the global structure. The generated winding syntax is transferred to the robots and allows the automatic winding of the six fiber layers.
In total, 36 individual elements were fabricated, whose geometries are based on structural principles abstracted from the beetle elytra. Each of them has an individual fiber layout which results in a material efficient load-bearing system.
The overall geometry demonstrates the morphologic adaptability of the system, by generating more complex spatial arrangements than a simple shell structure. Altogether the research pavilion shows how the computational synthesis of biological structural principles and the complex reciprocities between material, form and robotic fabrication can lead to the generation of innovative fiber composite construction methods. At the same time the multidisciplinary research approach not only leads to performative and material efficient lightweight constructions, it explores novel spatial qualities and expands the tectonic possibilities of architecture.