Integrated fabrication of permanent FRP formwork for free-form concrete members via 3D printing and automatic filament winding technologies

The increasing demand for architectural aesthetics has led to a rise in landmark structures featuring distinctive and geometrically complex concrete members. These free-form shapes present substantial challenges for conventional metal or timber formworks, which are costly and labor-intensive. To address these limitations, this study proposes an integrated fabrication workflow combining 3D printing and automatic fiber winding technologies to produce permanent, free-form fiber reinforced polymer (FRP) formworks for concrete structures. The workflow mainly involves: (1) 3D printing a polymer mandrel with the complex geometry; (2) automatically winding resin-impregnated fibers onto the mandrel with a computer-controlled system; (3) casting concrete into the FRP formwork to form the hybrid structural member. A case study involving the fabrication and testing of four variable-section prototype members confirmed the feasibility and efficiency of the proposed method. The case study provides a proof-of-concept route for typical free-form concrete structural members and the proposed technique offers an advantageous alternative to traditional formwork systems.