Abstract: Three sizes of T300 carbon fibres were selected for the preparation of triaxial woven fabric(TWF)resin-based composites with different pore sizes for concrete reinforcement. The three-dimensional displacement and strain fields were obtained using 3D-DIC technology, which visually reflected the evolution of the fabric expansion and shedding on the surface of the specimen and the strain extension of different yarns. The results show that the smaller the pore size of the triaxial fabric, the more significant the restraining effect of the carbon fibre triaxial fabric composite in compression. Compared with unconfined concrete, the peak load of TWF-24K was enhanced by 38.7%, TWF-12K by 41.2% and TWF-6K by 49.9%. At a certain porosity, the small pore size TWF enhances the compressive strength and ductility of concrete to a greater extent; the strain-time curves of TWF-6K specimens have more consistent trends and the stress distribution inside the specimens is more uniform. Combined with the 3D-DIC technique to obtain the displacement and strain field evolution laws for the whole time series from loading to damage, it shows that TWF-6K provides the best restraining effect compared to both TWF-12K and TWF-24K warp and weft yarns by evenly sharing the axial compression and radial tensile forces.

Key words: carbon fibre triaxial woven fabrics, concrete reinforcement, 3D-DIC, displacement field, 3D strain field, composites