Influence of gripper positions on the formation of wrinkles during the thermoforming process of thermoplastic UD-tape laminates

Thermoforming multiaxial UD fiber-reinforced thermoplastic tape laminates into complex geometries can lead to undesirable forming defects, such as out-of-plane wrinkles. These are detrimental to the performance of the resulting part and cannot be prevented by optimizing conventional process parameters alone. Other studies have therefore identified the introduction of membrane tension into the laminate during the forming stroke as an additional manipulation option to reduce wrinkling. The implementation of these membrane tensions is facilitated by the utilization of tension grippers, which can be positioned at various locations. To investigate the
extent to which the position of the grippers affects the forming result, a forming study was carried out. Three different gripper positioning configurations were defined and applied to the forming of the UD tape laminates. Using an industrial scale automated process, the laminates were both fully and partially formed into a complex geometry using each gripper configuration. To evaluate the influence of gripper positioning on the forming result, the components were 3D scanned and compared and evaluated in terms of their external contour, surface curvature and thickness distribution. ... mehrThe influence of the gripper configuration was demonstrated for all three variables investigated. Concurrently, the analysis revealed discernible correlations between the three variables examined. Areas with locally high surface curvature also showed local thickening at identical locations, and more uniform material feed resulted in lower surface curvature.