Tailored fibre placement (TFP) is an embroidery-based technology that allows the fibre tows to be placed exactly where they are most needed for structural performance and stitched into position on a compatible textile or polymer substrate. In this study commingled carbon-nylon fibre tows were utilised to produce thermoplastic cross-ply net-shaped preforms using TFP. Four TFP composite plaques were manufactured; baseline (blank), machined-hole, tailored-hole-1 and tailored-hole-2. Steering the tows was used to create the hole in tailored-hole-1 and tailored-hole-2. In comparison to the design of tailored-hole-1, a different fibre trajectory, with a circular reinforcement around the hole, was suggested for the tailored-hole-2. Fibre volume fraction, optical microscopy, X-ray-CT scans, tensile and open-hole tests were carried out. With the exception of the baseline sample, the modified design of tailored-hole-2 composite exhibited the highest axial strength and modulus compared to the machined-hole and tailored-hole-1 composites. Only the tailored-hole-2 specimens exhibited less than 10% reduction of the notched strength compared to the un-notched strength. This study highlights the importance of the stress/load-paths and associated fibre-orientations. While TFP can be an extremely valuable design tool for composite preforms and resulting structural components, a deep understanding of stress distributions is inevitable to achieve optimal TFP-design.

Thermoplastic composites are in high demand and continually growing in use due to their inherent properties. Commingled fibre is one of the recent solutions developed for thermoplastic composites, but has not yet ready for weaving. An alternative to commingling approach, co-weaving of reinforcing and thermoplastic fibres is investigated in this study. In this work, the carbon and nylon fibres were woven separately through the warp and weft directions, respectively. A 5-multilayer 3D weave architecture was designed to produce the co-woven fabrics. By varying the weft filling or pick density, a set of woven fabrics of different thermoplastic content was obtained. The hot press was used to consolidate the composite plaques. Samples of the thermoplastic composites were physically characterised through density, fibre volume fraction and void content and then optically investigated. The composite samples were also mechanically tested to determine the interlaminar shear strength via the short beam bending test. The result proves that co-weaving method for thermoplastic composites is a feasible approach as the composite shows a low void content of approximately 1.14 percent. Comparing the four co-woven composites tested in this study it is found that the maximum achievable strength (ILSS) is ~ 41.36MPa in the case of lowest matrix (PA66) and the highest fibre (CF) contents, i.e. 13PA/7CF.