Abstract: Fiber trajectories for conical shell surfaces are usually defined as geodesic path, fixed-angle path, and variable-angle path. Geodesic method has good laying quality, but it is not suitable for complex surfaces. Fixed angle method ensures that the tows have the same laying angle at any position, which guarantees the design strength of the laminate. However, it is prone to wrinkles and distortions on complex surfaces. General variable angle method is able to satisfy curvature constraints at any position without wrinkle defect. Therefore, in order to avoid defects such as wrinkles and buckling during fiber placement, a new variable angle trajectory planning algorithm for automatic fiber placement is proposed. On the basis of fixed-angle method and variable-angle method, the proportion factor is introduced, taking into account the design direction of the layer and the formation mechanism of wrinkle. The directional segmentation optimization of fixed-angle and variable-angle trajectories is achieved on the lay-up path, which solves the defects of single trajectory planning algorithm. Firstly, the geodesic curvatures of two paths are obtained based on the geometric relationship of the parameters of cone-shell flattened surface. Secondly, using the maximum curvature as the quality control criterion, an optimization method of lay-up trajectory is proposed. Then, taking the large taper cone shell as the model on which the lay-up trajectory simulation is carried out to complete the lay-up analysis. Finally, the proposed algorithm is verified by using AFP machine to conduct the lay-up test on the plane mold. The optimized trajectory combines the characteristics of fixed-angle trajectory and variable-angle trajectory, balancing the design strength of the components with lay-up quality. The design strength of the layer is achieved as much as possible while minimizing wrinkle defects.

Key words: automated fiber placement, trajectory planning, turning radius, wrinkle