Design and modelling of woven flax/bio-epoxy textile composite laminates for bridge decks

Pedestrian and cycle bridges constructed from concrete and steel pose sustainability challenges due to their high carbon emissions, susceptibility to corrosion, and high maintenance demands [1]. Textile fibre-reinforced polymer (FRP) composites provide lightweight, corrosion-resistant alternatives. Natural textile fibre-reinforced polymer (NFRP) composites further promote sustainability by using renewable fibres and reducing environmental impact. Their controllable textile architecture enables the tailoring of structural performance through laminate design and manufacturing. However, the structural behaviour of woven flax textile-reinforced bio-epoxy composites remains underexplored for bridge deck applications. This study evaluates the design and finite element modelling (FEM) of woven flax/bio-epoxy textile composite laminates for pedestrian and cycle bridge decks. The bridge design was inspired by the UK Network Rail Modular FRP FLOW Bridge [2]. A 3-D CAD model was developed in SolidWorks and analysed in Abaqus. Shell-based S4R element modelling with orthotropic material properties and hourglass control was employed. Symmetric [0/90]ₙ woven laminate lay-ups and woven-faced sandwich structures were investigated. A 2.5 kN/m² load with safety factors was applied in accordance with serviceability conditions [3]. The 32-layer trial laminate exhibited over-engineered stiffness, resulting in a mid-span displacement of Umax ≈ 4.53 mm. The optimized 16-layer [0/90]₈ laminate (≈ 21.4 mm) offered a better stiffness-weight ratio (Umax ≈ 18.44 mm; stress ≈ 15.74 MPa). A sandwich structure with 10 woven layers (≈ 13.4 mm) and a 9.5 mm balsa core exhibited a maximum displacement of Umax ≈ 22.6 mm while remaining within serviceability limits (≈ 22 mm) [3]. Hourglass energy remained below 1.3%, confirming model stability. Sensitivity analysis showed that mesh size and applied pressure load were the most significant factors in the structural behaviour. This study presents new design data for woven flax/bio-epoxy textile composite laminates, a material system rarely reported in the literature for bridge applications. This will inform the current and future experimental approaches.