The aerospace industry increasingly uses fibre-reinforced plastics that are manufactured using automated fibre placement (AFP). A common problem in AFP is the occurrence of gaps and overlaps that affect the structural perfromance of laminates. Tow width fluctuation is an important cause of gaps and overlaps. Two developments in manufacturing are combined to create a new mitigation method for gaps and overlaps. One development is fibre steering, which harnesses the flexibility of AFP to vary the fibre orientation within the ply. Another development is smart manufacturing which includes responding real-time to changes. The combination is local fibre steering which compensates for tow width fluctuation by placing tows adjacent to each other. In three steps it is assesed how effective local fibre steering is in increasing the structural performance of composite laminates by reducing gaps and overlaps through compensating for tow width fluctuation in automated fibre placement. Firstly, it is determined to what extent gaps and overlaps are reduced by constructing a conventional and a steered laminate. The tow width is modelled using a cubic spline. The steered laminate uses numerical approximations of the equations for parallel parametric curves. Two problems occurs that are: the accumulation of curvature leading to self-intersections and cusps, and large angle deviations. The curvature accumulation is tackled by using smoothing splines and the fibre angle deviation can be limited by taking a weighted average. Secondly, the tow width model is validated by measuring the tow width of two different materials. Thirdly, the effect of the reduction in gaps and overlaps and the fibre angle deviation on the structural performance is determined by using a finite element method based on the defect layer method that calculated the buckling load and the effective stiffness. Results show that gaps and overlaps cannot be completely eliminated but local fibre steering is able to increase the effective stiffness.

This report is the fourth and final report concluding the spring Design Synthesis Exercise for group 07. Ten bachelor students from the faculty of Aerospace Engineering at Delft University of Technology have worked eleven weeks on a given assignment: the design of an executive jet with amphibious capabilities. This report is aimed at peers, meaning basic engineering knowledge at the level of a third year bachelor student is assumed of the reader throughout the report...