The Hybrid Flax Pavilion demonstrates the application of an innovative wood and natural fiber hybrid construction system as an alternative to conventional building techniques. Developed by the Cluster of Excellence “Integrative Computational Design and Construction for Architecture” (IntCDC) at the University of Stuttgart, the pavilion was designed as a central exhibition space for the 2024 Landesgartenschau horticultural show on the banks of the Argen River in Wangen im Allgäu, Germany.
The hybrid system combines cross-laminated timber (CLT) and robotically wound flax fiber to craft a resource-efficient building made from regional and bio-based materials. Moreover, the pavilion’s design has a distinctly local connection — flax was originally processed in a historic spinning mill in the west of the city of Wangen (the mill has been renovated as part of the Landesgartenschau).
First hybrid structure to combine CLT and flax fiber
A permanent exhibition space, the Hybrid Flax Pavilion consists of an undulating roof structure and a circular glass facade that affords views in all directions. At the core of the pavilion, a climate garden serves as an inner courtyard and facilitates cross-ventilation and cooling. The building’s geothermally-activated floor slab is made from recycled concrete and low-carbon cement, ensuring year-round indoor comfort.
The three-dimensional roof is doubtless the pavilion’s standout feature. Produced using coreless flax filament winding, its construction is the first ever hybrid structure to combine cross-laminated timber plates with natural fiber bodies. The roof’s wave-like form is made from twenty hybrid components that alternate with regular timber plates, covering a 380-square-meter (4,090-square-feet) exhibition space. “The goal of this novel hybrid building system is to achieve expansive column-free space while minimizing material usage, thus leveraging the synergy between wood and natural fiber composites,” says IntCDC.
IntCDC developed a system that follows the principles of circular construction, ensuring materials can be separated, sorted, reused, and/or recycled.
The use of integrative computational methods (involving computer algorithms and simulations) in the pavilion’s design ensures the seamless assimilation of information from specialists across a range of disciplines, thus helping to connect research and industry. “This approach encompasses not only the design of hybrid fiber-timber components but also considers interfaces to conventional building elements like the facade and roof, taking into account their interconnected geometric and constructional requirements,” says IntCDC. A flexible and iterative design approach ensured adjustments could be made at every stage — the design, manufacturing, and construction of the pavilion was completed in just twelve months. “In the spirit of two-way knowledge transfer between cutting-edge research and construction companies, the building also shows how highly innovative architecture can be built by regional, small enterprises and skilled craftspeople,” adds IntCDC. With integrative computational design and precise prefabrication, the pavilion’s ceiling was assembled on-site in eight days.
A hybrid building system that uses natural fibers
The hybrid of flax fiber and timber maximizes the specialist qualities of both materials, creating lightweight, practical, and optimal building components. “The hybrid components aim to achieve a simply supported, beam-like structure with a variable structural height,” says IntCDC. “The fiber body forms a bottom surface that primarily bears tension loads, while the timber panel manages compression forces and constitutes the surface for the roof enclosure. Together they provide the strength and stiffness necessary to carry the high snow loads at the foothills of the Alps.”
The fiber body’s design comprises a series of sequentially wound natural flax fiber layers. IntCDC explains: “The primary spine layer aligns with the beam direction, acting as a bottom cord at the centre of the span. The fan layer gradually disperses loads to the edge supports, while the visually dominant lattice layers create a uniform fiber mesh to achieve the required structural integrity. Two additional corner reinforcement layers enhance fiber interaction and provide extra reinforcement in structurally critical areas.”
The fiber-timber hybrid components cover a span of 8.6 meters (28 feet) between linear supports. CLT panels with a thickness of 120 millimeters make up the primary framework and create the roof’s undulating aspect. The flax fiber bodies are attached with screws beneath every second CLT plate, thus making the hybrid components.
Bridging the gap between research and industry
A coreless filament winding process was used in the development and production of the fiber elements. Coreless filament winding is described as “a fabrication method that relies on the anisotropic mechanical properties of free-spanning fibers wound around supports in space to create efficient load bearing structures without requiring molds or dies” (Bodea, 2023). The winding frame is co-designed alongside the fiber element: “The element’s final fiber body emerges in the winding process as the equilibrium state of all fiber segments interacting,” says IntCDC. Its unique geometric form utilizes positive surface curvatures by employing areas of both positive and negative Gaussian curvature.
Here, “the winding frame includes a ‘spine’ that allows for the positive curvature of the component in its longitudinal direction as well as negative curvature, structural depth, and radius of curvature in its cross-section, all while providing the necessary structure to make the frame self-supporting,” explains IntCDC.
Tests on the geometry, fiber patterns, and fabrication processes were carried out at the University of Stuttgart using a 6-axis robotic arm with a custom end effector (something akin to giving the robot a hand and fingers). Once complete, the final design was transferred to an industrial partner for serial production using a 5-axis industrial filament winding machine. “Fabrication planning was directly integrated into the computational design process, streamlining the design-to-fabrication workflow and successfully bridging the gap between research and industry,” says IntCDC.
Professor Achim Menges, Director of Cluster of Excellence IntCDC, says: “The Hybrid Flax Pavilion is the result of many years of research and demonstrates how bio-based materials and bio-inspired structures can open up new avenues for regenerative and expressive architecture.”
Project partners
Cluster of Excellence IntCDC – Integrative Computational Design and Construction for Architecture, University of Stuttgart
Institute for Computational Design and Construction (ICD): Prof. Achim Menges, Rebeca Duque Estrada, Monika Göbel, Harrison Hildebrandt, Fabian Kannenberg, Christoph Schlopschnat, and Christoph Zechmeister
Institute of Building Structures and Structural Design (ITKE): Prof. Dr. Jan Knippers, Tzu-Ying Chen, Gregor Neubauer, Marta Gil Pérez, and Valentin Wagner
With support of: Daniel Bozo, Minghui Chen, Peter Ehvert, Alan Eskildsen, Alice Fleury, Sebastian Hügle, Niki Kentroti, Timo König, Laura Marsillo, Pascal Mindermann, Ivana Trifunovic, and Weiqi Xie
Landesgartenschau Wangen im Allgäu 2024 GmbH
Stadt Wangen im Allgäu
HA-CO Carbon GmbH: Siegbert Pachner, Dr. Oliver Fischer, and Danny Hummel
STERK abbundzentrum GmbH: Klaus Sterk, Franz Zodel, and Simon Sterk
FoWaTec GmbH: Sebastian Forster
Biedenkapp Stahlbau GmbH: Stefan Weidle, Markus Reischmann, and Frank Jahr
Harald Klein Erdbewegungen GmbH
Reference:
Bodea, S. (2023) Upscaled, robotic coreless filament winding methods for lightweight building elements for architecture, OPUS: Universität Stuttgart. Available at: http://dx.doi.org/10.18419/opus-13450 (Accessed: 29 May 2024).
