An experimental characterization of wrinkling generated during prepreg autoclave manufacturing using caul plates

Out-of-plane ply wrinkling is a major quality issue for carbon fiber reinforced prepreg parts. Its triggers are numerous and not every influencing parameter is fully understood, yet. The research presented in this paper aims at providing a better insight into ply wrinkling generated during autoclave compaction using caul plates. A detailed description of the experimental set-up and the applied methodology is provided. Statistical analyses of varying influencing factors such as part thickness, geometry, tool–part interaction, and laminate lay-up are presented. This, in turn, generates a better understanding of their impact on fiber wrinkling risk and size. Part geometry and compaction deformation show the most significant influence on wrinkle size. However, for the given manufacturing concept, tool–part interaction also plays a significant role. It influences both the dimension and location of the wrinkles, as well as the existence and size of a critical flange length of the part. A noteworthy effect on wrinkle generation and size can also be observed when adding unidirectional plies to an otherwise fabric laminate.

Study on Wrinkles during Rotary-Draw Bending Forming

The purpose of this research is to determine the state inside the material using finite-element analysis and to improve the performance of a rotary-draw bending forming by clarifying the mechanism of wrinkle generation. An analytical model of rotational drawing was made by using the general-purpose nonlinear finite-element analysis software MSC Marc, and the analytical results were compared with experimental results to verify the validity of the model. Furthermore, the mechanism of wrinkle generation was investigated. With the progress of processing, wrinkles occur not in the R part but in the original tube-side straight-tube part. The coefficient of friction between the tube material and the R portion of the bending mold promotes the occurrence of wrinkles and the growth of the generated wrinkles. Because wrinkles occur even if the friction coefficient between the tube material and bending mold R part is ignored, the generation condition of wrinkles also depends on parameters other than the friction coefficient.