The use of fibre-reinforced plastic composites (FRP) for lightweight construction solutions is becoming increasingly important. The processing of 2D scrims into complete 3D FRP components has been carried out with the help of complex manual assembly steps. The disadvantages of this procedure are distortions in the textile and, thus, deviations in the fibre alignments from the calculated load path. This paper presents a newly developed basic technology for the production of 3D reinforcing grids with variable warp and weft yarn section lengths based on multiaxial warp knitting technology. For this purpose, a new type of machine module and associated control technology for the production of weft yarn reserves on a multiaxial warp knitting machine was developed. In combination with technology from previous research work on the production of warp yarn lengths suitable for component contours, a basis was created for the production of 3D reinforcing grids.

The use of non-metallic, textile reinforcement structures in place of steel reinforcement is a key component in making concrete constructions more sustainable and durable than they currently are. The reason for this is the corrosion resistance of textile reinforcements, which makes it possible to reduce the thickness of the concrete cover and at the same time extend the service life of concrete structures. This reduces the amount of cement required and thus also the emission of the greenhouse gas carbon dioxide (CO2). By means of textile manufacturing technologies, customized, load-adapted reinforcement topologies can be adjusted to the requirements of highly stressed and well-designed concrete components. The objective of this paper is to give an overview of recent research literature dedicated to textile reinforcement structures that are already used for concrete applications in the construction industry as well as those currently under development. Therefore, textile reinforcement structures, which are divided into one-, two- and three-dimensional topologies, as well as common materials used for textile-reinforced concrete (TRC) are reviewed. Most research has so far been devoted to two-dimensional textile reinforcement structures. Furthermore, novel approaches to the fabrication of textile reinforcement structures for concrete applications based on robotic yarn deposition technologies are addressed.

Textile reinforcements have established themselves as a convincing alternative to conventional steel reinforcements in the building industry. In contrast to ribbed steel bars that ensure a stable mechanical interlock with concrete (form fit), the bonding force of smooth carbon rovings has so far been transmitted primarily by an adhesive bonding with the concrete matrix (material fit). However, this material fit does not enable the efficient use of the mechanical load capacity of the textile reinforcement. Solutions involving surface-profiled rods promise significant improvements in the bonding behavior by creating an additional mechanical interlock with the concrete matrix. An initial analysis was carried out to determine the effect of a braided rod geometry on the bonding behavior. For this purpose, novel braided rods with defined surface profiling consisting of several carbon filament yarns were developed and characterized in their tensile and bond properties. Further fundamental examinations to determine the influence of the impregnation as well as the application of a pre-tension during its consolidation in order to minimize the rod elongation under load were carried out. The investigations showed a high potential of the impregnated surface-profiled braided rods for a highly efficient application in concrete reinforcements. Hereby, a complete impregnation of the rod with a stiff polymer improved the tensile and bonding properties significantly. Compared to unprofiled reinforcement structures, the specific bonding stress could be increased up to 500% due to the strong form-fit effect of the braided rods while maintaining the high tensile properties.

A significant strategy to reduce the demand for natural resources and the associated environmental impact is enhanced material efficiency in the design process for new building structures. Innovative concepts for designing, modelling, constructing, producing and utilising sustainable resource-efficient concrete-based building components will be the foundation for future-oriented constructions. For this reason, the ability to process biologically inspired 3D textile reinforcement structures is crucial to fully exploit the potential of carbon concrete. This research project provides a fundamentally realigned, CAE-supported approach so that optimization algorithms, numerical models for the generation of robot placement paths and bionically induced yarn positioning can be taken into account. The evolved intelligent and modular yarn placement system forms the basis to overcome current challenges involved in the placing and stabilizing of spatial and highly branched reinforcement topologies during the manufacturing process. Hence, the novel tool-independent, geometrically highly variable, robot-supported fibre placement technology is supposed to be capable of manufacturing biologically inspired load adapted 3D textile topologies with reinforcement in z-direction.

Fibre-reinforced composites (FRCs) are already well established in several industrial sectors such as aerospace, automotive, plant engineering, shipbuilding and construction. The technical advantages of FRCs over metallic materials are well researched and proven. The key factors for an even wider industrial application of FRCs are the maximisation of resource and cost efficiency in the production and processing of the textile reinforcement materials. Due to its technology, warp knitting is the most productive and therefore cost-effective textile manufacturing process. In order to produce resource-efficient textile structures with these technologies, a high degree of prefabrication is required. This reduces costs by reducing the number of ply stacks, and by reducing the number of extra operations through final path and geometric yarn orientation of the preforms. It also reduces waste in post-processing. Furthermore, a high degree of prefabrication through functionalisation offers the potential to extend the application range of textile structures as purely mechanical reinforcements by integrating additional functions. So far, there is a gap in terms of an overview of the current state-of-the-art of relevant textile processes and products, which this work aims to fill. The focus of this work is therefore to provide an overview of warp knitted 3D structures.