Periodic Reporting for period 1 - FlexiForm (FlexiForm - Structurally and materially informed design and fabrication strategies for knitted textile formworks for concrete structures)
Berichtszeitraum: 2024-10-01 bis 2025-09-30
As emphasised by several EU initiatives, including the European Green Deal and the New European Bauhaus, reducing the construction industry’s impact on the global climate demands a drastic cut in CO2 emissions and raw material consumption, especially from concrete. A promising strategy is to design materially efficient structures that resist loads primarily through their geometry, following the principle of resistance through form.
Although modern digital design tools make it easy to design and analyse lightweight shell structures, their potential often remains untapped due to the difficulty of constructing complex double-curved concrete geometries. Conventional formwork methods, relying on single-use timber or milled foam, are wasteful, labour-intensive, and costly.
Fabric tensile formworks have gained attention for their structural efficiency and minimal material use. Among these, knitted textiles offer exceptional potential: they can be specified at the stitch level, enabling continuous double-curved formworks with tailored mechanical properties. This flexibility supports targeted meta-material designs and optimised fabrication. However, designing 3D knitted formworks that meet precise structural and functional requirements is a challenging task. It requires complex structural modelling and extensive prototyping, as their non-homogeneous behaviour is less predictable than that of woven textiles.
FlexiForm challenges these limitations by combining computational structural design and optimisation, digital fabrication, and automated construction into a unified workflow. This will enable the production of innovative, lightweight stay-in-place textile formworks using 3D knitting. 3D knitting is an innovative technique that enables the creation of seamless textiles with a wide range of custom knitting architectures. These knitted textile formworks will enable the straightforward construction of innovative, sustainable double-curved concrete shell structures that excel in material efficiency, mechanical functionality, embodied carbon reduction, reliability, and cost-effectiveness. In the future, we plan to expand this approach to include other materials, such as bio-based materials, which can pave the way for construction without relying on traditional cement.
Although modern digital design tools make it easy to design and analyse lightweight shell structures, their potential often remains untapped due to the difficulty of constructing complex double-curved concrete geometries. Conventional formwork methods, relying on single-use timber or milled foam, are wasteful, labour-intensive, and costly.
Fabric tensile formworks have gained attention for their structural efficiency and minimal material use. Among these, knitted textiles offer exceptional potential: they can be specified at the stitch level, enabling continuous double-curved formworks with tailored mechanical properties. This flexibility supports targeted meta-material designs and optimised fabrication. However, designing 3D knitted formworks that meet precise structural and functional requirements is a challenging task. It requires complex structural modelling and extensive prototyping, as their non-homogeneous behaviour is less predictable than that of woven textiles.
FlexiForm challenges these limitations by combining computational structural design and optimisation, digital fabrication, and automated construction into a unified workflow. This will enable the production of innovative, lightweight stay-in-place textile formworks using 3D knitting. 3D knitting is an innovative technique that enables the creation of seamless textiles with a wide range of custom knitting architectures. These knitted textile formworks will enable the straightforward construction of innovative, sustainable double-curved concrete shell structures that excel in material efficiency, mechanical functionality, embodied carbon reduction, reliability, and cost-effectiveness. In the future, we plan to expand this approach to include other materials, such as bio-based materials, which can pave the way for construction without relying on traditional cement.
FlexiForm comprises seven Work Packages (WP1–WP7), with WP2–WP4 forming the scientific core that underpins WP5, the demonstration phase. These foundational work packages respectively focus on material characterisation, fabrication workflows, and computational design, requiring close coordination to ensure consistency and integration across all research and development activities.
WP2 focuses on characterising and modelling the material behaviour of knitted textiles for use in flexible formworks. It comprises four tasks, with material selection and material testing completed, while mesoscale modelling is ongoing. Material selection prioritised sustainability, manufacturability, and mechanical performance, focusing on PES, rPET, and flax fibres, which were validated through prototypes such as the Necto Pavilion exhibited at the 2025 Venice Architecture Biennale. A custom biaxial testing rig was developed to evaluate weft-knitted textiles under both uniaxial and biaxial loading. Results demonstrate that knitting architecture significantly affects stiffness and deformation. These findings provide a strong basis for designing structurally efficient and sustainable textile formworks.
WP3 develops digital fabrication pipelines and material-aware pattern generation methods for knitted textile formworks. Although scheduled to start later in the project, several tasks commenced early to support the full-scale Necto Pavilion demonstrator.
WP4 aims to establish a computational form-finding framework for knitted textile formworks and to extend it to include the effects of concrete self-weight during casting. Initial work focused on developing the form-finding methodology, resulting in a multi-fidelity workflow that couples low-fidelity Force Density Method (FDM) models with high-fidelity Finite Element Method (FEM) simulations. This iterative process generates equilibrium geometries, refines them through stress analysis, and aligns mesh topology with principal stress trajectories to produce designs that are both structurally optimised and fabrication-ready.
WP5 will validate and demonstrate the FlexiForm workflow through the construction of a full-scale prototype, showcase its architectural and structural potential, and facilitate industry adoption. While not yet formally initiated, preparatory work is underway within WP2–WP4 and through the Necto Pavilion demonstrator, which serves as an early proof of concept for the integrated design-to-fabrication approach.
WP2 focuses on characterising and modelling the material behaviour of knitted textiles for use in flexible formworks. It comprises four tasks, with material selection and material testing completed, while mesoscale modelling is ongoing. Material selection prioritised sustainability, manufacturability, and mechanical performance, focusing on PES, rPET, and flax fibres, which were validated through prototypes such as the Necto Pavilion exhibited at the 2025 Venice Architecture Biennale. A custom biaxial testing rig was developed to evaluate weft-knitted textiles under both uniaxial and biaxial loading. Results demonstrate that knitting architecture significantly affects stiffness and deformation. These findings provide a strong basis for designing structurally efficient and sustainable textile formworks.
WP3 develops digital fabrication pipelines and material-aware pattern generation methods for knitted textile formworks. Although scheduled to start later in the project, several tasks commenced early to support the full-scale Necto Pavilion demonstrator.
WP4 aims to establish a computational form-finding framework for knitted textile formworks and to extend it to include the effects of concrete self-weight during casting. Initial work focused on developing the form-finding methodology, resulting in a multi-fidelity workflow that couples low-fidelity Force Density Method (FDM) models with high-fidelity Finite Element Method (FEM) simulations. This iterative process generates equilibrium geometries, refines them through stress analysis, and aligns mesh topology with principal stress trajectories to produce designs that are both structurally optimised and fabrication-ready.
WP5 will validate and demonstrate the FlexiForm workflow through the construction of a full-scale prototype, showcase its architectural and structural potential, and facilitate industry adoption. While not yet formally initiated, preparatory work is underway within WP2–WP4 and through the Necto Pavilion demonstrator, which serves as an early proof of concept for the integrated design-to-fabrication approach.
FlexiForm has established a solid foundation for the development of sustainable, materially efficient concrete construction methods by integrating computational design, digital fabrication, and advanced material research. Results from WP2–WP4 demonstrate significant progress toward a unified workflow for designing and producing knitted textile formworks: the characterisation of key materials (PES, rPET, flax fibres) and their mechanical properties has been completed; automated fabrication pipelines capable of transmitting machine-readable knitting instructions have been successfully tested and validated; and a multi-fidelity computational framework coupling FDM and FEM methods has been developed to enable geometry- and material-informed form-finding. These outcomes have been partially validated through the full-scale Necto Pavilion demonstrator at the 2025 Venice Architecture Biennale, showcasing the feasibility and architectural potential of the proposed approach. The anticipated impact includes substantial reductions in material waste, embodied carbon, and construction costs, as well as new opportunities for digital and circular fabrication in architecture and structural engineering. To ensure wider uptake and long-term success, further research and demonstration are needed to scale the workflow to diverse structural typologies and alternative materials, including bio-based composites.