Stuttgart University Showcase New Carbon Composite Pavilion

The Institute for Computational Design and the Institute of Building Structures and Structural Design of the University of Stuttgart have constructed another bionic research pavilion.

The new project is part of a successful series of research pavilions which showcase the potential of novel design, simulation and fabrication processes in architecture. The project was planned within one and a half years by students and researchers along with a team of biologists, paleontologists, architects and engineers.

The main focus was the development of a winding technique for modular, double layered fibre composite structures, which reduces the required formwork to a minimum while maintaining a large degree of geometric freedom. With help from the Institute of Evolution and Ecology and the department for Paleobiology of the University of Tübingen the team were able to develop a custom robotic fabrication method that were transferred into the making of the modular pavilion

During the investigation of natural lightweight structures, 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 fibre composite. The anisotropic characteristic of this material, which consists of chitin fibres embedded in a protein matrix, allows for locally differentiated material properties.

High resolution 3D models of various beetle elytra were extracted through micro-computed tomography. Together with SEM scans from the University of Tübingen, this enabled an analysis of the intricate internal structures of the beetle shell. The Elytra morphology is based on a double layered structure which is connected by column-like doubly curved support elements, the trabeculae. The fibre layout within a trabecula merges the upper and lower shell segments with continuous fibres. The distribution and geometric articulation of the trabecula is highly differentiated throughout the beetle shell. Through comparative studies of multiple flying beetle species the underlying structural principles could be identified and translated into design rules for structural morphologies.

Based on the differentiated trabeculae morphology and the individual fibre 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 fibre 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 fibre placement variation. Together with their unrestrained mouldability, fibre reinforced polymers are suitable to implement the complex geometries and material organisations of the abstracted natural construction principles. Conventional fabrication methods for fibre composite elements require a mould 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 moulds.

For the fabrication of the geometrically unique, double curved modules a robotic coreless winding method was developed, which uses two collaborating6-axis industrial robots to wind fibres between two custom-made steel frame effectors held by the robots. While the effectors define the edges of each component, the final geometry is emerging through the interaction of the subsequently laid fibres. The fibres are at first linearly tensioned between the two effector frames. The subsequently wound fibres lie on and tension each other which results in a reciprocal deformation. This fibre–fibre interaction generates doubly curved surfaces from initially straight deposited fibre connections. The order in which the resin impregnated fibre bundles (rovings) are wound onto the effectors is decisive for this process and is described through the winding syntax. The specific sequence of fibre winding allows to control the layout of every individual fibre 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 does not only save substantial resources through the needlessness of individual moulds, but in itself is a very material efficient fabrication process since there is no waste or cut-off pieces.

The specific robotic fabrication process includes the winding of 6 individual layers of glass and carbon fibres. A first glass fibre layer defines the elements geometry and serves as formwork for the subsequent carbon fibre layers. These carbon fibre layers act as structural reinforcement and are individually varied through the fibres anisotropic arrangement. The individual layout of the carbon fibres 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 6 fibre layers.

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