Planar Biaxial Tensile Testing of Weft-Knitted Textiles with Varying Knit Architectures

Abstract

Textiles are widely used in tensile structures due to their low weight, flexibility, and ability to span large areas efficiently through membrane action. Weft-knitted textiles, in particular, offer customization at a unit level, enabling the creation of locally programmable, 3D-shaped, continuous membranes. However, their mechanical characterization remains challenging, despite its importance for structural applications such as flexible formwork. This study examines the biaxial elastic properties of CNC weft-knitted textiles, focusing on the influence of knit architecture on their mechanical response. A custom biaxial tensile testing setup was developed to test three knitting patterns—interlock, tuck, and hexagonal—under three strain ratios (1:2, 1:1, and 2:1). Results show that stiffness varies significantly with knitting pattern and direction, reflecting asymmetries in textile microstructure. Strain distribution was also found to be non-uniform, with lower strains at the core than on the edges, highlighting the role of boundary conditions. Beyond providing insights into weft-knitted textile behaviour, this study contributes to an experimental framework for biaxial stiffness evaluation. The methodology serves as a proof-of-concept framework for the biaxial testing, test preparation, and result interpretation for knitted textiles, as well as for developing low-cost biaxial testing setups. These findings are particularly relevant for architectural and construction applications, where understanding the mechanical behaviour of knitted textiles is essential for structural integrity and design optimization.

Keywords: Tensile structures, Knitted textiles, Knit architecture, Biaxial tensile testing, Material characterization, Elastic properties