Process-parameter-dependent spring-in and warpage of locally reinforced ud tape laminates and V-shaped profiles

To take full advantage of the lightweight potential of thermoplastic advanced composites, a promising approach is the creation of tailored structures with locally reinforced, load bearing areas. However, especially in thin-walled structures this design strategy induces shape deformations due to the highly anisotropic material behavior of composites. In order to quantify these deviations, this paper presents a study on thin-walled tailored laminates made from thermoplastic unidirectional tape. Rectangular cross-ply layups were combined with a centered, longitudinal and unidirectional patch. The study covers the two relevant process stages of part manufacturing, which includes the consolidation of flat laminates and the subsequent forming of V-shaped profiles. To determine the influence of processing on the resulting spring-in and warpage, the forming pressure and mold temperature were varied on three levels. Based on characteristic geometric parameters, the results showed that tool temperature is the dominant influence, while forming pressure is of minor relevance. Furthermore, the underlying design of the experiments allowed the derivation of descriptive models to predict shape deformations with a high level of accuracy.