Abstract: Automatic fiber placement (AFP) technique is a critical manufacturing process to improve the efficiency of manufacturing components made of composite materials and reduce the cost. The AFP trajectory planning for ply layup is crucial to the quality of the fabrication process. For composite structure with complex contour, a justified placement technique is essential to ensure the manufacturability and the paving quality. In this paper, with a prototype of the simplified tail-cone structure in aft fuselage, different algorithms based on fixed angle, geodesic and variable angle methods are investigated for different layup orientations along a curved contour. The coverage and applicability of each algorithm are revealed and summarized. Conforming to the manufacturability along different layup orientations, the tail-cone prototype is automatically laid-up using prepreg slit tapes of 6.35 mm in width. The finite element analysis method is used to evaluate and validate the algorithms. The results show that the geodesic algorithm should be adopted for the 0° direction placement of tail-cone structure to reduce wrinkles. The fixed angle algorithm is good for the 90° direction layup to ensure continuous placement. To achieve a minimum gap at ±45° direction placement, a variable angle algorithm based on the results of the tow staggering test is adopted to divert the placement direction from the original one to the adjusted one which is closer to the geodesic direction in a curtain principle. For the conic structure, the fiber placement gap leads up to 30% reduction of the ply equivalent modulus and 10% reduction of the total strength. Therefore, the influential factors of AFP process on safety margin should be taken into account in the design of optimal structure.

Key words: composites, automatic fiber placement, trajectory planning, gap, finite element analysis