Tack of Thermoset Impregnated Carbon Fibers (TackTIC) – Characterization and Modeling of Prepreg-Tack for the Automated Production of CFRP Structures
Plastics Engineering
Final Report Abstract
The research project TackTIC aimed to generate a basic understanding of the influences and general adhesive mechanisms of the tackiness of pre-impregnated carbon fiber semi-finished products (prepregs). This material property is particularly important in the aircraft industry for the production of large-scale, high-strength fiber composite structural components using automated lay-up processes such as Automated Fiber Placement (AFP), as lay-up defects can occur in the laminate if the tack is insufficiently adjusted. In literature, prepreg tack has historically been investigated from segregated perspectives utilizing both diverse materials and measurement techniques eventually resulting in a lack of comparableness and transferability. There is evidence, however, to suggest that tack is a complex phenomenon that demands holistic consideration. The project TackTIC therefore explores the involved mechanisms (surface wetting, contact formation, autohesion), process and environmental influencing factors (compaction pressure, lay-up speed, ageing, temperature), material criteria (resin type, B-staging, toughening), measurement effects (probe, peel testing) and manufacturing implication of prepreg tack in AFP. Prepreg tack was found to be sensitive to all investigated influencing factors which could be ascribed to changes in material properties examined by comprehensive complementary material analysis. The employed measurement techniques were demonstrated to be suitable for prepreg tack measurement in terms of reproducibility and the ability to disclose adhesive mechanisms but were partially limited in terms of AFP process parameter representation. Therefore, the manufacturing implication of prepreg tack in AFP was assessed by utilizing a semi-empirical process model which was demonstrated to successfully replicate the characteristic bellshaped tack curves plotted as a function of prepreg temperature for different lay-up scenarios. Experimentally founded and model-based recommendations are furthermore proposed to tailor formulations of thermoplastic toughened epoxy-based prepreg resins with regard to tackiness. The presented outcomes of the project provide an informed basis for process adjustment to meet manufacturing demands in terms of prepreg tackiness and therefore reduce the risk of laminate defects during automated prepreg lay-up.
Publications
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Measuring techniques for prepreg tackiness: A comparative study, SAMPE Europe 23 Conference Proceedings, Euroforum El Escorial Madrid, Spain.
D. Budelmann, C. Schmidt & D. Meiners
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Adhesion-cohesion balance of prepreg tack in thermoset automated fiber placement. Part 1: Adhesion and surface wetting. Composites Part C: Open Access, 6, 100204.
Budelmann, D.; Schmidt, C. & Meiners, D.
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Haftungseigenschaften duromerer Kohlenstofffaser-Prepregs im Automated Fiber Placement. 4. Clausthaler Symposium Materialtechnik, 25.-26. Feb. 2021, Clausthal Zellerfeld.
D. Budelmann & D. Meiners
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Charakterisierung der Klebrigkeit von Prepregs: Implikationen für die automatisierte Herstellung von Luftfahrtstrukturen aus CFK. Science Days der TU Clausthal 2022: „Neuartige Materialien und Prozesse für wettbewerbsfähige Produkte“, 14. Sept. 2022, Clausthal Zellerfeld.
D. Budelmann & D. Meiners
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Tack of epoxy resin films for aerospace-grade prepregs: Influence of resin formulation, B-staging and toughening. Polymer Testing, 114, 107709.
Budelmann, D.; Schmidt, C. & Meiners, D.
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Adhesion-cohesion balance of prepreg tack in thermoset automated fiber placement. Part 2: Ply-ply cohesion through contact formation and autohesion. Composites Part C: Open Access, 12, 100396.
Budelmann, D.; Schmidt, C.; Steuernagel, L. & Meiners, D.
