In modern architecture branched supporting structures are increasingly used in roof and storey constructions. Until now, these branched columns can only be produced from steel in an extensive and cost-intensive way. A new and flexible construction made of fibre-reinforced plastic (FRP) as a hull around a concrete core makes it possible to produce a wide variety of different forms and geometries. The hull made of braided fibre-reinforced plastic serves as formwork and at the same time as reinforcement for the concrete. The nature of the different materials of hull and core are used advantageously: The fibres absorb tensile forces while the concrete absorbs compressive forces.
To manufacture FRP-knots with a load adapted fibre orientation a customised process to braid branched structures is required. Therefore, FRP jackets with different combinations of filler yarns and without filler yarns were produced on a 144 radial braiding machine. Enabling the potential of complex branched geometries with continuous load-confirming fibre arrangements over the entire braiding hull an advanced braiding technique to particularly create triaxially braided preforms is used. Subsequent to impregnation with a thermosetting resin and annealing, the textile preform is filled with concrete.
For the evaluation of the improvement in bearing strength due to the confinement of FRP-jacket on concrete and to analyse possible influences of fibre architecture, like braid angle of fibres, line-up with braided threads and number, allocation as well as concentration of filler yarns, on mechanical properties an experimental rig has been developed. In comparison to pure concrete specimens the mechanical parameters of fibre-reinforced plastic-concrete-composites show a high increase of bearing strength.