Flexural Behaviour of Carbon Textile-Reinforced Concrete with Prestress and Steel Fibres
Four-point bending tests were adopted to investigate the influences of the number of textile layers, volume content of steel fibres, and prestress on the flexural behaviour of carbon textile-reinforced concrete (TRC). The failure mode of the specimen changed from debonding failure to shear failure, accompanied by the matrix-textile interfacial debonding with an increasing number of textile layers. The interfacial bonding performance between the textile and matrix improved with the addition of steel fibres in the TRC specimens. The presence of prestress or steel fibres improved first-crack and ultimate stresses of the TRC specimen. In comparison with the first-crack stress, a more pronounced enhancement in the ultimate stress was achieved by the addition of steel fibres. However, the effect of prestress on the first-crack stress was found to be more significant than on the ultimate stress. The prestress combined with steel fibres further improved the flexural behaviour of the TRC specimens. The prestressed TRC specimens with 1% volume content of steel fibres effectively avoided debonding. Thus, the utilization of the textiles could be improved.
Pre-tensioning of Fabrics in Cement-based Composites
This paper studies the effects induced by applying a pre-tension load during the production of fabric–cement composites. The flexural behavior as well as the bonding between the different fabrics and the cement matrix was examined, as a means for characterizing the processing parameters. Microstructure characteristics of the fabric–matrix interface as well as the viscous elasticity properties of the fabrics were also explored and correlated with the mechanical properties of the composite. It was found that pre-tensioning of fabrics and the time at which the tension is removed can significantly influence the performance of the composite depending on yarn properties, mainly the viscous–elastic properties, and fabric geometry.
Shape and surface texture of molten droplets deposited on cold surfaces
When a molten droplet impacts on a cold surface, the interaction between solidification and fluid dynamics can lead to different shapes and surface textures of deposited droplets. This article presents an experimental study on deposition of small droplets (39 μm diameter) of molten wax ink on solid surfaces. Our results show that both the final shape and the surface texture of deposited droplets are extremely sensitive to deposition conditions, which include initial temperature of droplets, type of substrate surface and distance between substrate and printhead. Different surface textures are observed and shown to depend on the thermal and flow histories of ink droplets during the process of impact. A test using crystalline wax reveals crystallization as one of the major factors in determining the final texture.