Layup quality evaluation of fiber trajectory based on prepreg tow deformability for automated fiber placement

To conform to the fiber path, deformation of prepreg tow occurred inevitably in automated fiber placement process which would have great impact on layup quality. In order to evaluate whether fiber trajectory could be laid without prepreg distortion, fiber path layup quality was proposed and evaluated by prepreg tow deformation characteristic on free-form surface in this paper. Critical buckling radius of plane lateral bending was proposed as evaluation index for tow deformability. Layup quality of fiber trajectory was evaluated by the relationship between geodesic radius of trajectory and critical buckling radius. If the former radius was larger than the latter radius, layup quality of fiber path was fairly good, but not vice versa. A series of layup experiments were conducted to verify the evaluation criterion. Results showed that fiber trajectory layup quality could be well evaluated by this criterion proposed in this paper. And fiber modulus, prepreg thickness, and process parameters played important roles in determining fiber trajectory layup quality evaluated by prepreg deformability. By adjusting layup process parameters during automatic layup process, deformation ability of prepreg tow can be improved and the layup quality of fiber path could be enhanced to a higher level.