Processing and Microstructural Characterisation of Ultrathin Carbon/PEEK Tapes Produced via Slurry-Based Impregnation for Morphing Applications
J. Monney (TU Delft - Aerospace Engineering)
Marcello Righi – Mentor (Zurich University of Applied Science (ZHAW))
S. Upadhyay – Mentor (TU Delft - Aerospace Engineering)
C.A. Dransfeld – Mentor (TU Delft - Aerospace Engineering)
Gerald Piller – Graduation committee member
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Abstract
Many lightweight, high-performance applications have accelerated the adoption of carbon fibre-reinforced thermoplastic composites with thermoplastic matrices, particularly Polyetheretherketone (PEEK) matrices. However, manufacturing high-quality thermoplastic composite tapes remains challenging because high melt viscosity limits fibre impregnation. Wet powder impregnation addresses this by coating fibres with a water-based suspension of thermoplastic particles before consolidation.
This thesis investigates slurry-based manufacturing of unidirectional carbon/PEEK tapes. It relates process parameters and slurry state to tape quality by comparing two impregnation configurations: the Kiss-roller and Nip-roller processes. The investigation is structured around systematic manufacturing campaigns where key process parameters are varied. Line speed and creel tension are investigated for both impregnation routes, and the Nip gap is also varied for the Nip-roller configuration. Tape quality is assessed using gravimetric fibre volume fraction (FVF), while lateral tape quality indicators are computed over a rectangular region of interest (ROI) spanning the full tape width at the tape’s mid-length to quantify surface quality. Cross-section microscopy is used to support and bound the interpretation of surface-based metrics.
Within this dataset, the Kiss-roller process shows readable parametric trends. In Campaign 2, increasing line speed from 3.0 to 3.6 m/min systematically decreases FVF, with a smaller drop in speed sensitivity at higher creel tension. In contrast, the Nip-roller process is dominated by strong process variability, which limits the identification of monotonic effects of line speed or creel tension when conditions are not strictly repeated. In the most comparable subset (gap 35, L = 0), FVF ranges from 64.5–67.9% at 3.6 m/min and from 64.5–68.8% at 4.2 m/min. The spread within each speed is similar to the difference between speeds. In-process qualitative observations suggest that rapid inlet-regime transitions and tow spreading or overlap quality can yield distinct deposition states under similar setpoints.
Finally, microscopy highlights a key methodological limitation of surface-based analysis: tape quality indicators quantify lateral surface quality variations in the ROI but do not provide direct evidence of through-thickness impregnation. These data provide a consistent basis for discussing the trade-offs in controllability and reproducibility between the two impregnation routes. They show that robust parametric identification requires controlling slurry rheological state for the Kiss-roller process, where surface deposition behaviour is dominant, and stabilising inlet flow regime and tow spreading conditions for the Nip-roller process. Targeted microstructural validation is required when impregnation through the tape thickness governs mechanical reliability.