Cutting strategies of long fiber patch preforms for structures with complex fiber architecture

Load path optimized design is one way to reduce fiber consumption and therefore lead to lower manufacturing cost and weight. Continuous fibers in the form of rovings or tapes are typically placed according to load path. Typical technologies which are using this method (e.g. automated fiber placement or tailored fiber placement) are limited when it comes to small radii of curvature. The use of fiber patches with a specific length is an approach to overcome those limitations. A fiber tape is cut into patches which then can be placed independently in position and orientation of other patches. This enables high flexibility in fiber positioning. Since the patches are placed typically placed in a line, the size of gaps and overlaps between two neighboring patches of the same layer differs depending on the shape of the patch and the curvature of the allocated load path. Those gaps and overlaps are negatively influencing the mechanical properties and affect the impregnation behavior due to locally varying areal weight. One approach to avoid gaps and overlaps is to have a patch with a shape according to the load path trajectory. This paper presents studies on the influence of different patch geometries on tensile strength and stiffness and gives further insight into the failure mechanisms of patched laminates.