The Issue of the Tissue: Determining Feasible Robot Draping Sequences for Woven Prepreg Plies

In an effort to reduce cost in the manufacturing of composite parts for the aerospace industry, an automatic layup or draping solution is under development. By means of a grid of grippers, the robot system can pick-up entire woven prepreg plies and manipulate the plies onto double-curved mold surfaces of low curvature. This process is intended to substitute the current manual draping operation. Naturally, the quality requirements are the same, i.e. alignment of the ply within prescribed tolerances on the mold and zero wrinkling. Based on numerical simulations of the process and preliminary drape trials with the robot, it was concluded that the proper choice of robot draping sequences, i.e. gripper movements, is essential to meet the quality requirements. To this end, the current study attempts to generate such feasible draping sequences. The idea is to apply an approximate but computationally efficient ply model in an optimization framework where the gripper movements constitute the design variables. Rather than attempting to find the optimal draping sequences, the optimization criteria are chosen in a way that the generated drape movement will mimic the manual process. In this way, the solution space is greatly reduced.